So I've been playing a lot of PvP matches today.
The weapons and armour in the game at the moment have clearly only been designed with PvE in mind, i.e. it doesn't matter how anything handles, as long as you can kill stuff.
PvP right now is an exercise in frustration. It is rock paper scissors without the rock, and the scissors are also on fire.

Here are some notes (from a person with >200 ping).

1) NERF THE ANTIGUA SERIES.
High range. High damage. High firing speed. High clipsize. High bullet speed. No delay to attack. Doesn't stop you from moving.
Someone joins pvp with one of these, and they win. Even if there was a rock, these scissors would cut it. And you can't just buy one and fight back, because it's a super rare random-drop-only item!
In the meantime, don't use these guns or you are a jerk and no-one wants to play with you. :P

2) Guns, in general.
Some guns have weaknesses that just seem to be there for no reason. They have little to no importance in PvE, but attempting to hit another player and get away when you can't move or rotate for a few seconds will mean your death.
Hitting another player at all is quite hard with a high ping. I still haven't figured out exactly how to lead my shots to reliably hit anything faster than a jelly; hitting other players in motion is just impossible.

3) Armour.
It's been said before, but resistance is useless. You will be assimilated.
Ahem. It's very hard to tell whether or not your resistances are actually increasing your survivability, so it always feels like they aren't. There's no noticeable advantage to be gained with any armour.
Except the scissor suit, of course. It is made of scissors. Armours that give damage bonuses beat everything.

4) Jars and vials are annoying to use.
Picking up an explosive jar should be a good strategy but most of the time it just doesn't work. You might attack it instead, which could leave you vulnerable for quite a while if you're using a slow weapon. In order to be sure you're picking it up, you need to pause long enough to... leave you vulnerable. Hmm.
Selecting a vial from your belt seems to make you stop for a split second and, similarly, the computer seems to take a lot of coaxing and button mashing to actually select and to throw the thing.
Jars seem to be invisible if they were thrown from offscreen. Many times I have suddenly been hit by nothing and caught on fire.

5) Shields work both too well and not well enough.
As a person with >200 ping, I can't block anything. (especially not antigua shots.) I see something coming, I put my shield up, I see the force field, the bullet hits me, I get damaged anyway. Other people seem to be able to block everything. I have no idea how this could be fixed, but it just sucks.
I don't seem to be able to knock people back with my shield the way I can with monsters.

6) Fast weapons don't work.
It seems that due to mercy invincibility, weapons that have multiple attacks in a short time don't work in pvp. Only the first attack hits, and then the enemy is invincible for the rest. This is noticable with autoguns and cutters. Of course, antiguas fire slow enough that every shot can hit.

7) Multiple damage types don't work.
I've noticed that when a player is hit by a weapon that does two damage types, only one colour of damage indicator appears. Perhaps this is because the two damage types are applied as seperate attacks, and the player is invincible after the first one hits? Or is the display just wrong? It's hard to test when there's no numbers on anything.

8) Points / respawning
My first few pvp games seemed to consist of my score going 0 - 30 - 0 - 30 - 0 - 30 - 0 - 30, and I had no idea why. It's not immediately clear how many points you get/lose for what action. Losing points for dying seems strange with no health available.
I'd prefer if you didn't lose points for dying, and the penalty was instead a respawn timer. In addition, players could see where someone was about to respawn, and how soon. Instant respawns are problematic: I've been killed a few times by someone I'd just killed, who instantly appeared behind me with sword swinging.
I'd also like to see another method of making other players lose points.

9) No health available.
Perhaps this is just a bug, but the spots that used to spawn health now don't spawn anything. I'd like to see health made available, but maybe not directly.
Perhaps each level could contain at least one respawning monster crate, and when the monster dies it drops hearts. That way replenishing your health is something that you need to fight for, not run and hide.