I've been playing the pre-order beta.
So far I've not noticed any latency issues at all...though I'm not generally super-picky about that sort of thing.
Matchmaking works great. I've never had any trouble getting a group of real people quickly, and they are mostly able to carry their own weight.
I played Bardin enough to unlock all of his subclasses, and don't much care for any of them. None of his weapons have any reach, which means he can't really deal with crowds and can't damage enemies safely. Slayer has no survivability, and as much fun as spamming his leap-attack is, it's not enough damage or crowd control to really make him useful. His tank class can really take a beating, but there's little need for a tank in a game where the focus is mowing down hordes of vermin as quickly as possible. He might be more viable in the hardest difficulty, which I haven't tried yet.
I played Sienna enough to unlock her second class, which give her a homing fireball that is excellent for popping those special enemies, and comes with a fairly quick cooldown. The second class also comes with a talent that speeds up heat ventilation, allowing her to spam those staff attacks. Igniting swarms of vermin is always satisfying.
I only played Kerillian's first class so far. Her weapons have amazing reach and penetration, allowing her to shred swarms at close range. She also has some fun variety of bows, allowing varied play styles. My favorite right now is a poison bow whose arrows create clouds of poison, damaging and disabling groups of enemies. But she also has sniper bows and machine-gun bows.
I kinda hate the dust-filter that seems to cover the screen everywhere I look...I'll never understand why some game developers decide to do this crap to their own games. There's also a lot of fog and depth of field crap going on, but I was able to bypass that stuff with ReShade and get the game looking fairly pretty.
I see the game supports Tobii's eye-tracking thing, and now I'm kind of interested in that. It's hard to find reviews from people who actually have the gadget though, so I'm hesitant to shell out $150 for it.