Left 4 Dead 2, still a good game for good people
Left 4 Dead 2 is still a great purchase
Obviously the hype for L4D2 nowadays is completely non-existant, but the reasons that drove L4D into GOTY are all still there. And even better than before, because the players that stuck around are almost always friendly (unless you go into versus mode).
Nowadays if you run the game, you get a coop experience where the community is still big but experienced and rather calm, all of the official updates ever needed and a well developed steam workshop filled with mods and extra levels.
L4D2 is often on sale for 90% off it's regular price, so if you never tried it, get it when it's cheap and take it for a spin. Even if you fly solo, you're going to meet players with whom you'll want to group up often.
By the way, although L4D1 is still good and has it's darker, more serious tone, but the remaining players are often asshats and/or hackers, so unless you really feel the urge to check out the original, just stick with L4D2.)
I played and enjoyed that game so much. One of my first memorable coop experiences.
Even the bots were kind of usefull. Good old days :D