I hate games that require effort to be fun. LFD was great for around 4-6 or so hours. Then I'd completed all the campaigns. And as the depth of the actual gameplay was so shallow there really wasn't any need for me to go at it again. Versus just seemed a bit crap to me, in fact that crappy zombie mod for half life 2 was actually better for versus type gameplay.
Ok I admitt, I probable would have played for at least twice that long if I could have got into a decent group of people who played regularly, and bought myself a mic. But seriously, so much effort when all I need to do is log onto my 200hour cod 4 profile and I'm having fun within minutes. No crappy matchmaking and no waiting for other members to join me/set up voice comms etc.
So all in all I will have to say left 4 dead was one of the most overated, wastes of money I've ever spent. Left 4 dead 2, i may just check out if they make the gameplay a fair bit deeper.