The hold button and the two volume keys have shifted slightly up the side of the phone. There appears to be a couple of millimetres difference for the hold button, possibly less for the two volume buttons.
The change appears to have been made as the antenna seams have moved from the iPhone 4. The controversial antennas built into the side of the iPhone 4 suffered from loss of signal when held in a particular way, thanks to the way a hand stops the radio waves from getting through.
The antenna issue is one of the reasons we expected a more visibly updated design from Apple. We thought the company would want to draw a line under the palaver over the aerials and signal a new start, but the iPhone 4S is physically identical to its predecessor -- except for the change in the position of the buttons.
The change is a small one, but could be significant depending on the design of different cases. Cases usually have a small hole cut out of the side for the keys, while some rubberised cases allow you to press the buttons through soft indents. Depending how snugly the hole or indent fits around the buttons, the case could be misaligned. If you're buying a new case, it's an incentive to spend more on a new case made specially for the 4S, and could mean your current iPhone 4 case no longer fits.
But don't worry, that's -- if you'll pardon the pun -- the worse case scenario. Cases will hopefully fit fine. We'll dig out some cases and see if it's a problem when we get the 4S in for a full review later this week.
The iPhone 4S goes on sale in the UK this Friday at 8am. Will you be queuing up to bag yourself one? And if it's not a big enough upgrade to previous iPhones, see how the iPhone 4S shapes up against the iPhone 4 and iPhone 3GS.