I tried GameFly - I eventually gave it up. Not that it's bad, per say - it's far slower than netflix in terms of turnaround time and new popular games are almost impossible to get for rental right away (low availability) - but overall it works fine.
Yeah, I've done it before under a different account. I think that I will just hop on for a month to play Fallout 3 and then cancel. Hell, if I wanted to buy the game, the keep it now price is $50 so I would only lose about $5 on the deal.