I have been noticing them a while, mostly since trying to find live Mayer clips online, and seeing the recent DVD. The opening and closing scenes with him on some hill overlooking L.A. with a big body jazz Gibson and a Two Rock amp (and a line 6 delay/looper) is really nice to listen to and watch.

EDIT: That is a nice clip of what John is doing with his hands to study. My instructor is going to help me deconstruct some of his stuff and try to get into it, at least on an "easier" song like Gravity. Thanks for posting the clip!