I'm liking it. It's a lot more simplistic than L4D so the comparison isn't completely 1:1. It really is just wave based, park your ass in a room and unload until either them or you are dead. Welding doors is cool and offers some alternate strategy but largely you're just ripping through ammo and rearming in between waves.
The game is totally scalable for new enemies/weapons/maps. I hope the support is gonna be there.