Now that I have several pairs of FitFlops I can add some sizing recommendations.  The suede shoes seem to fit a tad looser and wider than the leather ones.  I have only bought styles with NO zippers as I prefer pull on.  Zippers can snag, let in cold and rain and are generally on shoes and boots that are tight around the ankles.  I prefer more room around the ankle.  I have a medium arch and have no trouble getting in and out of any of the FitFlop boots.  My regular size is 8 but I buy 9 in athletic shoes as I cannot stand to have my toes rub. FitFlops have plenty of room in the toe box; I have been ordering FitFlops in size 8 and they are plenty big, but I would not go down a whole size.  Your foot will flex as you walk and the extra space in length is a good thing.  FitFlops seem to run quite wide.  My size is Medium or B and the width on the suede is a little more than I would like.  The leather boots fit better for a medium width foot.  I definitely would not recommend FitFlops for someone with a very narrow foot, especially in suede.  Overall I like the leather better than the suede.  I also ordered the Mukluck style for around the house.  The Mukluks are even wider than the regular suede boot as they are synthetic fur lined in all parts of the boot except the foot bed.  The foot bed on the Mukluks is softer than the other FitFlop styles; more like a slipper......they are very nice and toasty.  FitFlops do NOT have arch supports or foot forming insoles which are a negative.  The inside foot bed is quite soft and flexible in all of the styles that I have tried and there is plenty of room to add orthotic inserts.  I am most comfortable with metatarsal frontal arch support which is almost impossible to find in any shoe.