I've had my share of spending 50 euros on a game you thought was goin to be cool to host and play it till your eyes bleed, but in fact it sucked arse big time.
I'm not gonna buy a multiplayer game more expensive then 20 euros unless I know for sure we're gonna host it and that it's cool.
The whole zombie thing is pretty hard to make a good game with. The only ones who succeeded in my eyes are resident evil and FEAR. They're both single player games (the FEAR multiplayer was an epic fail lads, don't wanna talk about that). I have strong doubts to think that l4d will be one of them.
My advise to you is donate some of your precious money to SpA. We'll have our new server earlier that way. That means that we will have room for a complete other game soon. That means we can launch a new game server as soon as we find something that we think is worth hosting. When we finally set our minds to that, and some of us have bought the game, you could buy the same game.
I played it at the GC in this nice fancy bus.
And I can tell you it is REALLY good. We had to wait like 3 times 10 minutes for the previous group but the 10 minutes we got felt like merely 1 minute. It was really intense and this AI thingie which controls the zombie flow really works. It was a really tense experiance.
And apart from this being coöp, it will also feature single player gameplay -> you play the maps alone rather then in coop.
Any way I was really sceptical about it at first and thought that shooting zombies really could not be 'fun' and was more like brainless shooting, but I think Valve really nailed it this time.