I downloaded the Left 4 Dead 2 Demo last night. It didn't work. I updated my drivers and reinstalled and nothing. I wasn't about to wipe Steam just for a demo... even if that Demo is Left 4 Dead 2. I didn't feel like fighting it anymore.
So I ended up playing Aion all night, which was fun. I got to do another run through The Training Grounds which is a level 25-30 instance in the Abyss.