Gaikai has announced (via VG247) that they've acquired Mass Effect 3 and are the only streaming service to do so. A demo is also availabe so any skeptics can start of their browser and give it a go.
I've never used Gaikai, but I can attest to having what I thought was a pretty great experience demoing Batman: Arkham City on Gaikai competitor OnLive. I played the first half hour or so of the game and it ran no slowdown whatsoever and didn't look bad. I'd be a subscriber right now if the service had games I actually want to play and don't already have on console.
I think that's what's ultimately holding that style of gaming back: a lack of industry backing. But I definitely support it myself, I'm excited to see how it evolves (If it works this well right now…) and I can't wait to try this.