ok, speaking as a winmillion user here:

High movement speed when using it needs to be mastered, or you'll throw yourself into danger regularly

Charge attack can be re-aimed during the animation, or cancelled completely by blocking at any point.

The bullets winmillion creates cause Wolvers, Devilites and Gremlins to dodge, and mechaknights to shield. This is a major issue against wolvers, devilites and mechaknights - not so much for gremlins.

The time before you can block on each swing is longer than you'd think.

If you can't consistently land both the energy disc and slash, you'll do less damage in tier 2 than with the 3* arc razor, and less damage in 4* than any other sword.

Pretty much I wouldn't recommend using it.

There are better weapons for jelly runs, simply by nature of having special effects or shadow damage.

It's certainly useable there, but until the 5* version comes out, I'd hold on getting it to 4*

I FAVOR the Winmillion. Everyone doesn't like it because it is hard to use and easy to master. But once you get used to the potential it has, it can become a deadly weapon.
Here is what I recommend you having as you class set up.

1.) Winmillion
2.) Gun (preferably a 6 shooter)
3.) Swift Strike Buckler (You must have your attack speed to "high" or higher. (I know, painful right? But I say don't rely on your shield to block enemies attacks. Just use the shield to bounce back the enemies.)
4.) DON'T use the full nooby vog set. Use Skolver Set instead. It makes up for the damage. Or better yet, use Skolver Coat and Vog Cap. It is a lot better if you can't get used to the 3* shield.
5.) Make sure AutoAim is turned off in your settings. (Don't rely on auto aim. Rely on true skill aiming.)

With this set up, you'll own!
Ok, this is how you use a winmillion when dealing with enemies:

Basic Enemies (Like jellys) - Throw swings in bursts of 2, then block (Also known as Block Cancel), then switch weapons, shoot a few rounds with your gun, switch to your winmillion and then repeat.
Wolvers (mostly them), Devilites, and Gremlins - Taunt the Wolvers by shooting your gun randomly. Make sure they dodge to a corner or wait when they start barking. When they are at a corner just kill them with the "Winmillion Attack" technique. When they bark, they are defenseless! If your near them, attack them with the "Winmillion Attack." If your far away from them, shoot them like 2 times while running towards them, then attack them with the "Winmillion Attack!"
RoboSpiral Knights - Yeah the block their shield when you start attacking them. But they are so easy to deal with. Just shoot one shot of your gun so that the Robos can block. Run up to them, then when they are done blocking (when their shield goes red), just attack them!

In PvP:
Recommended Classes:
Recon or Striker works both well. It is all about preference. And remember to use that Technique I taught you!!!

In Conclusion:
Overall, the Winmillion isn't favored much, because it isn't newbie friendly. I understand that. But the Winmillion isn't ment for 3-hit combos or special attacks. It is used for short fast bursts, that allows you to push back the enemy away before they strike you. I really like this sword compared to those nooby, over-powered, over-used Avenger/Faust swords (Those lame swords require little skill. It is easy to learn and master, which I don't like.).

One thing in favor of the spur line is it actually works very well as a 4th slot weapon for an otherwise dedicated gunslinger or demoknight. With the other 3 slots covering damage types or a range of status effects, having a sword to break out of crowds or burst down minerals and bushes is helpful and the forward momentum and projectile on the winmillion help it shine there, although in that case it's purely for utility and not damage so a spur or arc razor works just as well as the winmillion but are a great deal cheaper. The line's relative lack of popularity insures getting a hold of one with a nice ASI uv to really get out of jams fast without altering the rest of your loadout won't break your bank in half too, especially compared to the direct competition for the slot, a ctr calibur.

Ok i tried to translate what Matoro said.
"Use a wooden stick instead of a sharp knive to cut your bread. Cause that's how the pro-gamer do it."

I think the effort does not match with the effect. But even so, i want to try out his tactic, just to see how much effort is required :-)

Whats the upside of the Winmillion vs Final Flourish for example?

And if the winmillion fires spikes, how far do they go?

If I am to use an arsenal with a sword majority, then Winmillion would be my option as a ranged weapon. Although I would use it for range rather as a main weapon. I am going to acquire a variety of swords, like the Glacius, Acheron, and Cold Iron V. and possibly the Winmillion. However, the Winmillion is something I am never going to use to fight Wolvers, I rather use the Wild Hunting Blade (WHB). Even though piercing weapons like the Flourish and Snarble Barb work, I have a Snarble Barb by the way, I would rather use the WHB because using the rapiers is alittle awkward for me. Plus I do prefer landing more hits on fast moving adversaries like the Wolvers. This is mostly preference of mine, the Winmillion could be of usefulness in certain areas and with different weapon combinations.
I have yet to actually have access to T3 depths, nor do I have 4-star rating weapons (still crafting 3-star equipment and experimenting). However from what I know about the Winmillion is that it can shoot blade beams, and still hit like any sword in the game. So does this mean I can hit both from a distance and melee? It appears so, which means that I could use the Winmillion to eliminate gun puppies that are in a spot where I cannot approach them safely, or perhaps approach a horde of enemies with the Winmillion's combo just to get the last hit to land and knock back the enemies (this is also called a Beat) and then hold my attack button for an inverted lunge-- basically go into the process to prepare a charge attack with the intention to move and be able to send more blade beams at my opponents for crowd control.
In combination with the weapons I want. A shield is always useful for the ability to shield bump opponents to create distance for the Winmillion's ranged shockwaves, the idea is to use a shield to make distance and be on the move when taking the offensive as I would plan. I already have a Graviton Charge with the intention to create the G. Vortex for further usage. As Winmillion's ranged energy beams provoke the enemies into attacking me, that gives control of where they are going and therefore lead them into the Graviton Vortex intended to hoard them all in one place using the shield bumping technique to make sure none come out of its detonation radius. The Winmillion could also be useful in combination with the Cold Iron Vanquisher (CIV). The CIV is personal choice for slaying the Undead (most definetly Candlestick if I have to), but the usefulness comes from approaching a mob with a charged attack; a spin attack that knocks back any enemy hit by it and creating some breathing room to use the Winmillion-- although this is a riskier alternative to the shield bump>Winmillion beams but its a more offensive approach in the sense that I could land big hits on multiple enemies in a crowd first and then execute a keep away strategy for the rest of the fight.
These are mostly ideas that I have in mind on how I would use the Winmillion more effectively. Every sword has its strength and weaknesses but the effectiveness is also determined by the player's skill and how its used in combination to the rest of the equipment. My intention is to discover what can and cannot do with the Winmillion; a sword is a sword, I can still kill a mook without the necessity to use its ranged-attacks. In addition to applying Beats and Lunges for expanded usage, I could intentionally use the finisher to knock away enemies, or charge my weapon so I can have another moment to fire more projectiles. It doesn't take much effort for me to come up with tactics on how to use two weapons effectively; the challenge is actually pulling it off. It is not impossible to use the G. Vortex to keep crowds in check, just have to find that moment where I can charge the bomb and place it. Winmillion would be used to poke Wolvers into attacking me, so I can use the WHB. The Winmillion is one of the only weapons with the ability to shoot projectiles and melee at the same time, and it has versatile potential.

Winmillion is a waste of cr/CE. Any 4* sword will do a better job at handling enemies in tier 3. I actually played with a winmillion user once, and they said that the DMG SUCKED (they were wearing a full Snarby set with a flower.)
Speaking of this, could someone come up with damage of winmillion in tier 3? (any depth is fine) I am really curious, and it will put the sword in better perspective.
I'll he honest, I actually considered getting his sword and a bomb (sword/gun in one and a bomb as auxiliary weapon), but the idea got shot down b/c of it's crappiness.
PS: Vs slimes:
Think of it this way. Its like getting a cautery sword to fight slimes instead of a nightblade. Completely pointless.