Interesting exercise. Here are my stats:

Out of 11.957 shots over the last 3 years my top 7 are:

ISO 140: 0.91% <- gotta be an auto ISO setting!
ISO 200: 29.77%
ISO 400: 36.9%
ISO 640: 3.34%
ISO 800: 3.54%
ISO 1000: 1.41%
ISO 1250: 1.2%
ISO 1600: 5.23%

My general philosophy is to use the lowest ISO where I can get a reasonable shutter speed for the shot I am trying to get. And a lot of that reasoning has to do with the noise factor of using higher ISO settings. And the majority of the higher ISO settings I think have come from the few times I set the camera on auto ISO. I wasn't real happy with what I saw on my screen afterwards. I don't do a whole lot of printing, either. Cameras are getting better, and using higher ISO's is getting more common, but with the gear that I have right now, keeping it as low as possible works better for me right now. I'm getting better at having my monopod or tripod handy, and using them more, but not all the time either.