Just watched this on my phone this morning and it's pretty awesome.
Mayer gives us a bit of insight into how this cover came to be and how he made it his own which is WAY more interesting than just covering the original note-for-note.
He also talks about how he got the specific tone for his version of Crossroads and I found that fascinating.
Joe Satriani, Steve Vai and a number of other guitar greats have often said that things "just happen" in studio. So the lesson, it seems, is to get jamming and recording to see what "comes out".