I agree - sheer enthusiasm and get it done attitude makes up and then some more for raw brainpower.

Something else that is important in the context of compatible personality is someone who is very direct and critical when needed.

That's a good point. The ability to disagree well is useful. I'd rather work with someone who won't automatically rubber-stamp everything I say but instead, when he disagrees, can argue his points in a clear and well-informed way. It is rather satisfying to be proven wrong and learn something in the process.

A friend of mine who works at Goog since the early days has noted several times that he frequently feels like the dumbest person in the room. He's quite bright and probably would be the smartest person in MOST rooms.

I think I would rather work somewhere I would feel like the dumbest person in the room than the smartest.