I wouldn't necessarily call it "disappointing", but I'm a big Jason Isbell fan since his days in Drive-By Truckers. When I saw him last year in Minneapolis, he basically played note-for-note replications of his studio tracks, and never really improvised or shredded much on his guitar (and the guy can really play). It was powerful, and competent but it kind of lacked that ragged glory/energy of a great rock and roll show, and I know the guy is more than capable of that sort of performance. His playing in the Twin Cities or DSM is no longer in the "must see" category it once was for me.