i sized down 1 from my normal dress shoe size and they fit perfect. some people have sized down a half size and have found them to fit perfect. some have worn them true to size and they fit perfect.
this tells me that there is something else going on than just the number--it depends on the shape of your foot. my advice: order from zappos, sizing down 1/2. if you need them bigger, go true to size. if you need them smaller, go down 1.