Michael Angelo once said those who put fast playing down do so because they can't play fast themselves.
There's some who call themselves shredders who suck (Great Kat anyone?) but you can't argue with players like Petrucci and Malmsteen. Even Herman Li from Dragonforce manages to astound me and they're not that big yet.
Can I just point out I hate jazz and think it's the most pointless excuse for not knowing what you're actually doing.