He is mostly playing the pentatonic/blues scale these days. He's just playing it in a bunch of different positions up and down the neck. Sometimes he adds a few different notes here and there (often the 2nd and 6th) to make more of a dorian sound and to add colour to what he's playing.

In wheel he uses minor arpeggios and the dorian mode alot, thats one of his best solos melodically.

One of his most melodically interesting solos to me was the one he played in Come Back To Bed on ACL. It goes through both the major and minor pentatonic scales. The first part is in F#m and then he kicks into the bluesier stuff at the end with the A blues scale. It has some great melodic peaks.