This has probably been beaten to death but I thought I'd put in my two cents. Working in a repair shop for these phones all day, I can say with all certainty that using an iPhone 4 display can be used in place of a 4S display. What we have done when we ran out of the 4S displays is substituted with a Verizon iPhone 4 display. We use that one because the hold-down legs are nearly identical except for one which is impeded by the sim card slot on the 4S. We just simply snip that one off and everything else bolts in properly. As stated above by a few people, the ambient light sensor does not work as the 4S has a different location for it.