I had a sunny day where both of my lenses fogged like crazy, which was a surprise since I'd never had it happen before. I put them both by the fire to dry out for a day and we are back in business. Awesome goggles.
I reckon the I/O is a sick google. they seem so expensive tho, but when i see a deal i am definately gonna snag a pair because of this thread! so many lenses and so easy to change!