Steam opened the floodgates last night. You probably snuck over to Best Buy to pick up a retail copy on your lunch break. Have you had a chance to pop into Valve's zombie sequel yet? I reviewed the game for G4 (and, as you might expected, loved it), which means I've already dumped many more hours into Left 4 Dead 2 than you have! Take that, Internet. But you'll all surpass me soon enough.
If you've been able to give it a spin, what do you think so far?