I never have problems with my sizing (5.5 / 6) my feet are quite narrow and even when the reviews say to size up, I don't do it and never had any problems.  Ive been wearing them for two days straight trying to break them and although they do fit, they are a bit tight, so maybe sizing up will make them feel more comfortable.  I guess Ill never know if 6.5 woul be too big. Other than this they are gorgeous and pretty warm, definitely what I was looking for.