I watched a couple of clips: a Comedy Central show, a Fort Minor video (from Warner Brothers), and a Sports Illustrated swimsuit model profile. The video quality is pretty good. Definitely a couple of steps above YouTube. It still came up lacking, especially with the swimsuit model! It was tolerable for the other two shows.
The responsiveness was very good for me, but I do have a very fast connection (8 mbps) at home. Everything seemed really smooth and impressive. Obviously there's not a lot of content on there. I showed it to my wife this morning, and she was less than impressed. I think if the MTV channel would have had Pimp My Ride on it, then she might have been a little impressed.