I personally think iPad YouTube app's touch is not too bad; but in general (not limited to YouTube), I think the UI design of web video players are all too fixated on the existing design.
For example, when not in fullscreen mode, I don't see why all the controls need to be confined to the video frame and disappear when not hovering. While this design choice has its benefits, it also presents significant drawbacks: it obscures the actual content when you're interacting with the controls (a problem that's particularly acute on smaller screens), and performing quick, repetitive actions becomes difficult because the controls aren't visible until you hover over them, among other issues. This approach to web video player UI has been a pet peeve of mine for some time.