I finally got myself Left4Dead after realizing it's much cheaper in GBP, so, since Steam doesn't allow Euro countries to pay in Pounds, we asked a friend of our to buy them as a gift. So the price isn't even annoying anymore.
After playing 42 hours Left 4 Dead, I have come to find a few annoyances: Recycled textures and models (from HL2, CSS) - so they didn't even bother making new models (for that price!!). Some of the sounds are recycled, too. And the four campaigns each taking an hour or so, is way too little to play. So, basically they sold a mod priced like a standalone game. I'm so glad I didn't preorder.
The good side of the game is the co-op fun. It's so much fun having to trust other players to watch ones' back. I had a few scares. And I still panic when the Tanks growls somewhere near us. Sneaking by the witch is always creepy, especially if one of the team happens to like to startle the witch rather than just sneak. The Achievements are fun but annoying to reach. Trying to headshot a jumping Hunter is pretty hard. I haven't even tried Versus mode, since I'm co-op in every game!
So, in conclusion: I like the game, but I'm still disappointed.