OnLive By Digital FoundryEurogamer's Digital Foundry has an extremely in-depth analysis of the OnLive service today, and it seemingly tells you everything you'd want to know--performance, image quality, lag, pricing. If you're interested in the service, or have any questions, this is the place to go. If you're tremendously lazy (who isn't?), here's a useful bit:
A good rule of thumb with OnLive picture quality (and indeed streaming video in general) is that the more the image changes from one frame to the next, the lower the quality of the resultant encoded image. So, third-person adventure titles like Assassin's Creed II, Prince of Persia: The Forgotten Sands, Splinter Cell: Conviction and Batman: Arkham Asylum are pretty good picks on OnLive's behalf, in theory. However, racing games and twitch-based first person shooters are shifting the entire world view pretty much every frame, so the picture quality looks poor whenever you're in motion, which is most of the time.
I will say this: overall, OnLive has done a better job than I thought they would. It's not something I'd want, but it's not a total train wreck, either.
I'm just waiting for the showdown between ISPs and content providers, because it should be coming very, very soon. The issue of bandwidth caps has to be resolved.