EDIT: Does anyone want a game of Left 4 Dead? Capmaign, I hate versus. I'm going to start one soon (in about ~30 minutes)? Tomorrow i think i want to play one as well (between 11am-2PM PST).
Campaign is a lot more fun to me, I mean, if I want to play a FPS against other people, I play something else than a game sold as a coop game. I found the infected to be barely controllable, and playing as the survivors to be a PITA and really tough. I added people to my friends' list, people that I met playing L4D early on when I got it, and now whenever I click "join their game" I end up in a versus game. They all switched to versus.
It's hard to join friends in a game though, most of the time, games fill up quickly. You pretty much have to plan it in advance.