As a producer, Kanye is great: he had the best beats on the Black Album (which was very dope by the way, and i'm not a Jay-z fan at all), College Dropout was one of the best produced album of 2004 and he reached his peak with Common's Be (best mainstream hip hop album of the year so far).
Those who say that he only speed up and loop soul vocals need to listen more closely. College Dropeout was full of live instrumentations, choirs and additional vocals and the beats were kinda complex. Plus his drums programmation are real nice. With Be, he proved he could incorporate boom bap elements to his beats (listen to "The Corner" or "Chi City"). He can also produce classic soul (and not techno r&b) material like his tracks on the John Legend album.
As an emcee, i guess it is a love it or hate it thing. His delivery is special but i'm feeling his sense of humor.
Of course you can hate the man (he looks like an asshole to me). But i got high expectation for his upcoming album (the single is fire + with Common and John Legend in his team, dude can't go wrong)