On long days at work, sometimes my pinky will start to ache from holding down control while typing. It's definitely better than leaving Ctrl at the bottom left, but I'm considering remapping the left Alt to Ctrl so I can type it with my thumb. (No other RSI symptoms, and I'd like to keep it that way.)

I don't have a Kinesis keyboard, but I read that their modifier keys (along with space, Enter, and backspace) are all at the thumbs, and that seems like a really good idea.