PC Perspective has an exclusive preview of the OnLive gaming service, you can read it over here. This cloud game service is still in beta phase, and the reviewer is left with mixed feelings. For slower paced games it seemed to work well, but with other games input lag prevented a smooth gaming experience.
Obviously the games that didn't work were the fast paced shooter games: Unreal Tournament 3, Crysis and even Call of Juarez. If you are an avid PC gamer you will likely be very disappointed by the experience, both in terms of image quality and input latency, of playing these types of games using OnLive. This is especially true if you use a keyboard and mouse - using a game pad did mute the adverse effects quite a bit and made the game (and my apparent skill) more acceptable.