They are comfortable.  I was expecting for them to feel weird with material between each toe but they do not.  As others have said, you should measure your foot using the process outlined on Vibram's website; however, if your second toe, the one next to your big toe, is longer than your big toe you will definitely need to order a pair one size larger. I ordered the size the website told me to and had to exchange them for one size larger which fits perfectly.