The first few times that I ran barefoot or with Five Fingers I found that my calves were sore afterwards. Definitely some different muscle action!
Mine seem to be okay, but not sure if that's because I tried to stay off road. I think on days I have energy I'm quite a forefootstriker anyway, but I'm not really sure. It was interesting, but am definitely not adding barefoot running to my list of things to do right now!