I'm in the market for an iPhone 4S to replace my older iPhone and iPod. If I took a Christmas holiday in America, the cost of a US phone is substantially less than a UK phone at current exchange rates.
However, there's a possibility that there's physical differences between the UK model and the US version that would make the US version impractical in the UK. I know that the range of bands used for cellular comms in the UK differs somewhat from in the US.
So, is the iPhone 4S built to only a single design that can handle the differing frequencies used throughout Apple's main markets, meaning that a SIM-free one will work anywhere regardless of where it was bought? Or is each model tailored to a particular region's cellular specifications, making a US bought iPhone all but useless in the UK?