The graphics were about the same as the Zune HD and framerates felt pretty consistent -- overall, we'd place what we saw next to the PSP, but obviously we didn't do any real testing or comparisons here.
It's great that you could control XBMC from your PSP, but what if your XBOX isn't on, and your TV isn't on, and your TV is not on the right input?? You still have to get up or find the remote and adjust all of that...