I've had to clean up after one of those guys. He'd crank out the first cut of a codebase, and I'd go through and factor out the instant cruft his stream of consciousness had spewed out. We actually made a pretty good team.
He was (still is) brilliant, but his codebase would quickly degenerate into an inmaintainable plate of spaghetti without someone like me, and he knew it. He told me as much.