Just had my first go, started single player where you get 3 computer controlled helpers (there are 4 main characters).
Then i discovered you can also play co-op online, with 3 other players. I played that, but since there is no tutorial or so, i was sometimes a bit clueless on how to do this or how to use that. Not that it required rocketscience.
So if anyone else is going to give it a shot: post something here and we can try to arrange to play together. Always nicer to shoot zombies with people who you know and probably can trust. As in 'accidentally put you on fire' instead of 'put you on fire on purpose'. Like mentioned somewhere, friendly fire is indeed on
On a positive note, Shiny digs the game, so we'll probably be picking up the full version. If nothing else at least she and I can play it. And if we're lucky one of you guys as well.