If its like OnLive, where I'm 300 miles from the server, out here on the cali central coast, it won't look so hot. For example, a 3rd person action game like Batman... the player controlled character will look pretty sharp, then depending on your bandwidth, everything radiating outward from your character will get more and more pixelated to the point of looking like utter crap. Take the PS3's low res textures, upscaled to say 1080p, then pixelated due to bandwidth/latency... It's not very pretty to be honest.
As in all things, YMMV, and if the price is right, it's better than watching a "let's play" on youtube.