The concept of OnLive sounds cool to me. I'm a bit ignorant in this regard, but I think it's essentially a thin-client?
Biggest drawback is that you're essentially renting the games. Even the ones you pay full price for could disappear after a few years. That's a big enough reason for me to say no thanks.
-Deozaan
Yeah, im still a little scepticle...would be nice if it gave you the licence keys to be able to download a version of the game for playing if the service dies.
The client its self is very small, and its a pretty quick service on your PC, I cant comment on the TV Box thing they have as I dont own it, however tempted I am to get it

I must say, im very tempted to upgrade to the monthly subscription, purely cause $10 USD a month aint much to lose, and if I dont want it after the first free month, I simply cancel and lose no money.
Its handy to try out games for 30 mins though as its not like a typical demo, its just...play 30 mins of the actual game, from the very beginning...granted, this doesnt give you much info about some games (like is FO:NV was on it...30 mins would be pointless) but for some others, its good to do it as you can get a feel for the REAL game, not some demo thrown out by the company which sometimes doesnt even represent actual game missions and such.