The sonics on the few discs I've listened to so far are very good. I've heard Discs 5,6, and 7 covering his work with Boz Scaggs, Herbie Mann, and the ABB, and they sound GREAT. Kudo's to the engineer and producer.
Skydog
Is a seven-CD box set tracing his slide guitar virtuosity from his earliest days to his last, just thought I would mention. Interview with his Daughter on NPR