I've never seen adults on heelys. I was tempted to buy some cause they sell adult sizes at Journeys but then I remembered how I am a total klutz and will probably end up breaking my ass and thought otherwise.
Crocs have got to be the ugliest shoes I've ever seen. As a female I probably would never wear them out unless I worked a desk job where no one would have to see my feet. But the people that I know who have them say they are incredibly comfortable.