I love these sandals! I wear a 9.5 in street shoes and wear a 9 in Chacos so i would say go a half size down, especially for skinny feet like I have. Only grief I have is once adujsted properly that the strap for tightning the sandal drags the ground and I step on it all the time. Had to do a little custom fabricating to prevent it from fraying from walking on it.
I have a bad right knee and the sandals support my feet really well and improve my stride so I can walk further without pain, which is a huge plus for a pair of sandals!