Yeah, I tried it a few months ago.
Its very strange, and I wouldn't class it as a game, its more of a sim. Everything in SL is user-created, right down to the clothes you wear, to actual buildings, vehicles and just about anything you can think of. The graphics are pretty decent, but its really tough on your connection, even on 2mb broadband.
Its like a cross between The Sims and those VR-headset games that we saw on the tv when Virtual Reality first came out. But, unless you're interested in learning how to build things, put designs onto things, or make scripts that make items interactive, there isn't actually a lot to do - you just find yourself wandering around a huge map looking at things.