I had it for like seven or eight months, and it's only good if you're willing to play games that have been out for a while and aren't in high demand. I was never able to get a new release, only older games that weren't high on my gaming list in the first place.
I canceled it because I could easily go to BlockBuster and rent a game for cheaper probably. It was like $16.95 a month I think, and I was only using it for like one game a month, which is pretty ridiculous.
If you have a lot of time, and can beat a game in a few days and send it back, it could be worth it. Chances are though, if the game was worth playing almost nonstop until you beat it, you would have bought it in the first place.