Some changes to the antennas, though not the basic design (steel bands around the outside body of the phone, introduced in iPhone 4). Apple has given few details about this but , says the 4S seems to have received the tweaks made with the release in early 2011 of the first CDMA iPhone 4 on Verizon. The 4S thus “likewise includes what appears to be a combination of Rx [radio receive] diversity and the ability to switch between antennas for transmit.” Apple says this lets the 4S “intelligently switch between the [two] antennas for even better call quality.”

Camera and “mirroring”:

A much improved camera, not just the 8-megpixel sensor (versus 5 megapixels for iPhone 4). But a new image signal processor designed by Apple and a bunch of other improvements to support 1080p photos and video recording, faster camera setup and picture sequences, and better quality photos compared to iPhone 4.

AirPlay Mirroring, a feature imported from iPad 2, letting you display what’s on your phone’s screen on a flat-panel display via Apple TV.

User Interface: