Is the worth picking up for single player?
Probably not. The only thing you'd be able to enjoy is the Horde-like, Survival Blitz mode. It's fun - but probably not worth the price of admission.
Just some random impressions so far -
I've had very few games with noticeable lag - though there have been times when my stealth attack misses despite me sitting there spamming it. It's really damn annoying.
Had a problem where I'd get disconnected at the end of every match which meant that I had to wait to jump into a new one. The problem disappeared after a few games.
I applaud the developers for coming straight out and saying they'd do some balancing depending on feedback. The team was probably smart enough to realize that they wouldn't be able to get it right on the first try. The Support class seems overpowered. The ability to push with bots, a shotgun, and an overpowered turret is just too much for one class. It's like combining the Engineer and the Medic from Killzone 2. Makes for a great support class - but they end up scoring more kills than most other classes which I think strays from the idea of support.
Tons of Gunners out there. I feel like they're slightly overpowered though, to be honest, I haven't played as one yet so I can't tell you what kind of problems they face.
The Sniper seems pretty well balanced. Traps, an AoE grenade, good sniping potential, as well as a weak close-up game was a good mix.
The Assassin, the class I play as the most, seems to weakest. I like the idea of regenerating stealth @ level 3 - but I think the rate is a bit too slow. Their stealth is too easily negated with the large number of gunners out there. Making it so they pwn Jackbots was a nice touch. Maybe I just need to adjust my playstyle a bit. She's a lot of fun though.
Overall a fun game, but I have doubts about how long it will last. I'd be surprised if the community makes it through the summer. It's too bad because it's a fun little title. A shame when titles like this and even Snoopy Flying Ace have such short legs. Still - worth the price if you're into team-based shooters.