I usually wear 9M but after reading the reviews I purchased a 9 1/2M which fits with my heel peeking over just a tot.  However, since its leather I believe that I am comfortable with the 9 1/2.  The 9 would have been too small and narrow at the toe.  On the other hand I just love the style of the shoe.  It looks great on my feet.  I cannot accurately speak much to the comfort or arch support of it since I have not worn it yet.