I've used various vnc connections over the years, and still have one I use on a local server. They're fine for doing document editing etc., but not great. Good luck passing though sound or video though.

The big joke with cloud based OS is that you're going to need a local cpu to run it, so you might as well run a local OS. Even if it got to the point where it was just i/o connected to a remote pc, latency is going to be a bitch for any real world application short of office work.