It's basically facebook for games, has some nice features to keep track of your friends and what they play, game collection etc. It also hooks into PSN and XBL to get updates on what you are playing. Worth a look.
Every so often, I consider joining.
I would have quite a job on my hands entering my game library though
and the site does not come across as bandwidth-friendly.
I like the up to date info it retreives from Xbox Live and PSN. At least I know if my friends are bullsh*ting me when they say they're playing Borderlands without me while im stuck at work :P