I generally find interacting with people (NT or otherwise) to be approximately as tiring as programming a computer; it's fun for short periods of time and a serious effort for long periods of time, though still often rewarding in the latter case. I almost answered this question by saying that social interaction wasn't tiring, but reevaluated after realizing that I've just grown used to it; other people's behavior is impossible to explain unless they find social interaction significantly less tiring than I do.

I'm not a complete introvert, but I do lean in that general direction.