I had an obsession with his music a couple of years ago, and i still love it. I think both his music and lyrics are great, and quite original. I've got nothing against his performance of his songs, either. I think his spontaneous/intuitive feeling performances usually makes his songs stand out on their own (without any fancy arrangements and such). Although I could agree that some of his songs may suit tighter musicianship and more sophisticated arrangements. I'm a fan of both. Whatever suits the songs.
I really relate to his personality, and after watching "The Devil and Daniel Johnston", I thought of him as a more fragile and unstable version of myself. So I guess he's an INFP. Though, "a very, very, sadly unbalanced one", as purplewool said.