The shoes seem to run a little on the narrow size, if I had known this I would have gotten a size bigger.  While they are very comfortable, I don't know that I would do any serious cross training (Crossfit/P90X) in them as they are very warm.  Even taking long walks in the warmer weather will cause your feet to get very hot and sweat.  Not a lot of ventilation in them.  They are however very good for short training sessions.  Support on the arch and sides is very good.  I bought them to replace my light workout shoes and they're too warm for that, so they've turned into my walking shoes.