I know what you mean with that, although I think it's more stylistic than unintentional (if you're refering to the nasal thingy he does). Try and find the songs Where Do We Go, Super Tuesday, and A Better World. The vocals are a bit smoother.
Oddly enough, it's not the nasalnes that bugs me. I think it's more the smoothnes of his voice, it just sounds like some young guy with a smooth voice trying to imitate classic rock.