Well, I have no problems with the latency since I don't like Online Mode games. So I usually play Solo Games and in that case, the latency is not a big worry.
What I don't like in these systems is that you only get a few months to play each title before they take it out from the catalogue and replace it with another game...
Yep, that's the main thing I thought of that makes a lot of these services disappointing. The single player side of things didn't bother me much, a few hiccups here and there aren't much different to regular frame drops that might take place on a desktop. It's really impressive that you can play these games through a browser though.