Agreed. Similar instance, used to work with this great developer. He was very talented, friendly, etc. Used to pair with him every day and he challenged me constantly to improve. He also tried to challenge the rest of the team, questioning the way we did things and suggesting ways to improve. He collided with a few guys who'd been there longer. Layoffs came around and he got canned. Now though, he's better off and works at a place that encourages continual improvement.

Sometimes though, the "who is a superstar" becomes "who is your competition" and then it becomes a negative. At least when competition is feared instead of seen as a challenge.