I played in the closed alpha with a bunch of friends, I think there were about 6-7 of us in total who had codes. It has very much nailed the L4D vibe. The card thing they have is actually well done. The difficulty is high, but there are a lot of viable ways to play (you can become an OP melee machine, focus on support use, be a tank, a gunner, whatever). We played on Classic, the easiest setting with zero friendly fire, and only beat the last level once (some of the guys beat it already when I wasn't playing, so we all beat it at least once in about 6-7 attempts, sometimes with randoms). Having limited continues is a bitch that I'm not personally fond of at the easiest level where you're trying to just get used to the game. Very few gameplay bugs at the moment and only one trivial (and quite frankly funny) visual bug I've seen so far. They still have six months to go and I expect that will be further balancing of the difficulties and additional levels more than bug fixing based on what we've seen so far.

I think the early stages of each act are very well balanced, the last mission is a bitch but I think it could have been handled better tactically by our team... but then again, maybe not, as we used tactics that so far all the wins I've seen used, which involve suicide runs by two people. I'm pretty sure it would still be possible to finish it if everyone sticks together but it was only on closed alpha for a short time.

Very much looking forward to playing it again. It's awesome fun. If it weren't for knowing they need to put in more than just the first act, I'd say they could release it now and it'd still be far more polished than any other similar game out there at the moment.