I like his upright playing, but his upright tone doesn't do it for me.
There's a lot of, well, noise in it. It just has some je ne sais quoi, some harshness that sounds bad to my ear.
Of course, the 'orrible tweeters on his SWR rig (used for his electric playing) are harsh to the point of pain.
But hey, you've got to love a guy that invites my kids back stage, and I certainly love his music. And he can play whatever kind of instrument he wants-- but I'd be surprised if he doesn't tour with the red bass.