I normally wear a 12 and these ran half a size too big for me.  For comparison, my Adidas NEO sneakers fit perfectly in a 12.  I also tried these on in an 11.5 at a local store and they fit fine length wise.  The biggest problem I have with the Superstars, and this was evident in the 11.5 and 12 sizes, is that they don't fit snuggly around the ankle and heel.  Even tying them tight through the last pair of shoelace holes, my heels would lift out of the shoes too much as I walked.  Walking was possible but it didn't feel right or secure.  Even fully tied up, I could easily pull these shoes off my feet.  I think maybe the opening on these shoes is too large.  It's unfortunate, because I really like the style and durable construction of these shoes.  I hope Adidas addresses the loose heel fit on these.