I used to wear size 10.  I ordered this in 11.  This pair feels just a tad too big, if that makes sense.  I'm afraid of returning these and ordering 10.5, so I'm keeping these.  I guess my new NB size is 11 (mirthless laugh).  These are sneakers (compared to mx 621), and they have that sinking feeling at the toe, but other brands do as well, I found out recently.  The sole does not feel rock hard like mx623.  I use gel insert anyway, but I can wear these without the inserts for a time.