I always wear a 6.5 M. That's what I ordered and received, however the toe box is very wide and with the memory foam insole, the front of my foot moves around a lot. It seems like it may cause rubbing and blisters. I might return, but haven't decided yet. Great price and good looking shoe, though!
UPDATE: I decided to keep the shoes. If I lace them up to the top (use all shoelace eyelets) and make sure that I keep the it tied loosely, the lace and ankle area does not cut into my ankle and the shoe does not allow my foot to slide around in the toe box. They are comfortable and I'm sure they'll be better after they're broken in some more.
Reebok was founded for one of the best reasons possible: athletes wanted to run faster. So in the 1890s, joseph william Foster made some of the first known running shoes with spikes in them. By 1895, he was in business making shoes by hand for top runners; and before long his fledgling company, j.W. Foster and sons, developed an international clientele of distinguished athletes.