Things I love about the new arena, and things that just don't work...
This new arena is, as I see it, a mixed bag. There are some things that I was VERY pleased to see, but then on the other hand there were some things that disappointed me. The following is my attempt to lay out both the good and the bad without getting as emotional as... say... I was immediately after each and every match. *cough* Sorry to everyone who had to see that in-game, by the way...
the Good:
Crown entry fee. Very inexpensive crown entry fee! A player could spend their mist energy dungeoning up some crowns and with what they earn there they could spend all evening in the arena and not run out of cash.
Token distribution: This surprised me the most, and the most pleasantly. I LOVE that participating in the match to its end always gives you a krogmo coin even if you lose, and that winning only gives you an additional one (plus some kind of bonus? I don't even know. We activate the bonus every time but I have yet to win it myself). This means that as long as a person keeps playing, they can earn the prizes only a little slower than the people actually managing to win.
Prizes mostly being recipes. They can be sold, they can be used to craft unbound 3* equipment that can then be sold (or given to friends), even right now on the first day these items appear to usually run something like 25000 at the auction (compared to about 15000 for normal 3* gear). It is good to see that we won't have to buy pre-made, bind-on-acquire weapons like the other token rewards to date. If a person doesn't care for the arena they can still reasonably acquire the new stuff, as opposed to having to run the same boss over and over until they're completely sick of it. I mean, I want some quicksilver gear but I've already done Roarmulus SO many times just to get two of the weapons, I just.. I don't like doing the same thing over and over again. So yeah...
the Bad:
People will spawn right next to you. They are invincible for quite a while after this happens, but they are IMMEDIATELY able to plant a bomb. This means that you will be taking cover from a bomb, only to have someone appear right next to you and immediately get to kill you for free while they remain immune to their own bomb, your bombs, and whatever bombs you were hiding from at the time. This is incredibly frustrating.
Poor hit detection. It's not even an issue of lag (though people have told me that's an issue too). I can be fully behind cover, not moving, and still get killed by a blast going through the adjacent square. I'm sorry, but bomberman styled games only work if you only get killed by the attacks that actually HIT you.
Can we walk through the bombs? Can we not? There is no consistency in this. Sometimes we get trapped on the bombs, sometimes we walk right through them. This needs to be a lot more consistent for this to work at all.
Lack of Strategic/Special power-ups. It's just a little boring and predictable (apart from the things that aren't working consistently) when the only power ups are speed, bomb count, and bomb power. What made Bomberman really fun was that one person would pick up a bomb-kicking or throwing power up, or be inflicted with the diarrhea curse, or short fuses. Without that sort of game-changing power ups, it's just cut-and-dry plant bombs at open spaces in rows and then hide, over and over.
It really annoys me how being on top of a bomb can get you stuck on stuff.
The value of those recipes is far below the current market price; a player that has an equal distribution of placings in games (one 1st and one 2nd per 8 games) then it only costs around 3k for 50 coins. Expect to see those prices drop. The players good enough to pvp for profit will be wiling to sell the 3* recipes at the market price for 3* recipes in general, and the 5* recipes could happily go for 10k and still make a slight profit for even the average user I mentioned before, so they won't go much above the base price (25k) of regular 5* recipes once the buyer market catches on to how much they're really worth. Still decent money, but the prices won't stay this high.
Though I don't see much value in some of the recipes, namely the bombs. We already have an elemental shock bomb, and we don't really need a bomb with stun as long as we have shivermist. I feel the electron vortex should be shadow like the bomb it's based on, to give a status effect to a shadow bomb.
At the lack of strategic powerups, that could be a point, though remember all of those were added to bomberman as the series evolved. Right now we have a more retro bomberman; it may evolve over time. The bugs will likely be fixed eventually (3 bug fixes already!), and better lag correction may be implemented sometime. Basically, what you see as problems may all be fixed in due time. Except maybe players spawning next to you (which may be handwaved as giving bad players a chance)
To me, the best parts of the arena are the profit margins for decent players, and the fact it'll slowly leech crowns out of the game, causing inflation. Also Triglav looks awesome, and the trinkets bring decent value to trinket slot at last.
Oh, and Blast Network's really fun, especially for the more oldschool gamers.
The Electron Vortex is Elemental because there isn't currently a direct-damage elemental damage bomb in the game otherwise. The Shock bomb that we got with the new boss is a Haze-type bomb, which means initial damage is petty pathetic because the point of it is to apply a status effect, not actually kill stuff. I'm sorry to hear that it's more like the Graviton ones, and not like the Spine cone or Blast bomb, but bombers basically don't have a strong option for dealing with Constructs and Undead right now, unlike everyone else who has at least one decent weapon both are weak against.
The Haze line is another matter entirely. I think I've already mentioned elsewhere that there are a few specific advantages to using Stun as opposed to Freeze, although I can't find my old post about it.
Wait, no, I found it. So rather than repeat myself:
http://forums.spiralknights.com/en/node/17980#comment-101924
Yeah, I'd be happy to see one of the new 5* Haze bombs in my parties.
Sadly, I have nothing new to add to the list of things I love about the arena, but a few major things I need to add to the disappointment list:
CREDIT FOR THE KILLS:
This keeps happening to me. I'll expertly box somebody in with a bomb, and what do they do? They plant one of their own bombs between themself and my bomb. When my bomb goes off, instead of killing them directly, it sets off their bomb and that kills them. They get a death, but cheat me out of my kill. I've had matches where I've killed half a dozen people and wound up with a kill count of 0 because of people kill stealing THEMSELVES.
SERIOUSLY, THAT WALKING OVER BOMBS THING:
People are somehow blocking my movement by dropping bombs into squares I just moved OUT of. If I am moving to the right, and someone drops a bomb in the square to the left of me, why does this block me from continuing to move right but still let me move left or down? (of course, they put bombs in those spaces, too)
PEOPLE MOVING FASTER THAN FASTEST:
How exactly are people managing to outrun me after I've collected the maximum level of speed power-ups? Armor effects don't work here, right? If someone is wearing 5* quicksilver gear underneath their costume armor, that isn't going to actually give them a speed boost in Blast Network, is it?
PEOPLE SUICIDING AND INSTA-SPAWNING FOR FREE KILLS:
The match starts. Somebody immediately jumps on his own bomb, pays the energy fee, spawns INVINCIBLE next to someone else and gets to kill them for free. They start the match with one death and one kill while making sure someone else starts with one death and zero kills. This kind of exploit needs to be fixed.
THE LAST HALF OF THE MATCH, TOO MUCH EMPTY SPACE:
About halfway through the match, all of the destructible blocks are long destructed and there is a LOT of empty space. At this point, the match has already been decided. Whoever has the most blast-area and bomb count power-ups cannot possibly lose because they can just spam entire-screen-covering bombs constantly, killing everyone as soon as their spawn invulnerability wears off, and no one can possibly get close enough to them to try and attack them because they are all spawning slow with a single one-square-blast bomb and the guy whose blasts are covering the entire field is making sure all of the power-ups stay destroyed.
TOO MANY PEOPLE IN A MATCH:
Generally, all of this spawning on top of each other business wouldn't be happening if they weren't trying to cram as many of us into each arena session as possible. It also worsens the "one guy with all the power ups who can never be stopped" problem because he's just got that many powerless people, confused because they're trying not to get killed by each other, who can't possibly help but run into his bombs. Once that guy gets into the lead in points, he is guarunteed to win because even if someone COULD manage to kill him, he's already thirty points ahead of everyone else from getting kills with every single bomb he drops. It's impossible for anyone to ever catch up to his score no matter how hard they try. Take a lesson from classic bomberman games: Have between four and six people in the arena, never more than that.

Mist spawns should be removed, or you should respawn where you died, like on PVE. I vote 6 people per match.

Poor hit detection. It's not even an issue of lag (though people have told me that's an issue too). I can be fully behind cover, not moving, and still get killed by a blast going through the adjacent square. I'm sorry, but bomberman styled games only work if you only get killed by the attacks that actually HIT you.
Part of this is because our movement in Blast Network is not tile-based.
Can we walk through the bombs? Can we not? There is no consistency in this. Sometimes we get trapped on the bombs, sometimes we walk right through them. This needs to be a lot more consistent for this to work at all.
This is probably due to lag. I think you should play as if you're 1 tile movement behind where YOU see where you are. It'll save a lot of heartache :x
[edit] This is my original response to that, because I thought you meant the blast - but it's cool anyway, if you wanna be a showoff and do awesome dodge tricks LOL
There is consistency. Instead of an instant blast that blows up and stays "alive" in a row/column, the blast actually sets off 1 block at a time. When the "head" of the blast passes you, then you can walk through it, kinda like this (and pardon the terrible illustration, I didn't want to make a gif of it, so I just used Paint7):
http://i.imgur.com/966pF.png
The blue star is you and the red diamonds are the "dangerous" part of the bomb. Of course in the actual game, the dangerous part might be more than 1 tile large, but regardless, there's enough time to be able to step 2 tiles over, making it look like you just invincible-hacked through an impossible situation.
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I think that other than the power ups, the three other things NEED to be fixed. Better power ups would be a secondary thing. I agree with you completely though. Sometimes I die when I'm even a tile away from a bomb blast and then... dead. You can't walk through bombs, but they need to make that better too. I hate when someone escapes a bomb, and then when I'm trapped I really am trapped. I've only had people spawn next to me at the beginning of the match, but what happens is, we both die because we both place bombs to get out at two different spots, and trap ourselves. Even so, the pros are much more significant than the cons, even now. Knowing that it can get better with easy fixes is great (Hopefully OOO fixes some of those things).