Are you as sure of that as your assertion that the behavior of scroll bars in Lion/Mountain Lion is not different, just the appearance?
In Snow Leopard, the clickable area is, IIRC, slightly smaller than the actual size of the window widgets. It's possible to click the widget without triggering it. That's not possible in Lion/Mountain Lion.
Don't get me wrong: I'm not trying to disparage your opinion on the changes Apple has made. I can understand why the changes could be unwelcome, but we need to be accurate on the information being distributed. I could be wrong on the clickable area of the window widgets. I tried to Google the subject, but couldn't get anything one way or the other.
Hugh: we're discussing, at this point, whether or not the scroll bars in Snow Leopard and earlier have the same disappearing behavior as the new scroll bars in Lion/Mountain Lion, which they don't.