I've never cared for it myself, but I remember Louie Armstrong bopping out the sounds that way; he was much better at playing the trumpet.
I'd say he did it all quite well.
Watched 'Tap' last night with Gregory Hines and there's a scene featuring Joe Morton (Brother From Another Planet) going into a fierce manic-like scat while the crime he's part of is taking place. It's a creepy scene but the scatting was superb.
