If I caved in against my better judgement, and bought myself a shiny new iPhone, then can the SIM be used in another (unlocked) phone? As far as my limited knowledge of mobile stuff goes, that's generally OK with other phones/SIMs, but I'd better check about the iPhone SIM specifically before I spend any cash... The reason I'd want to do that, in case anyone is wondering, is that I do a bit of travelling and I know the iPhone just plain won't work in some countries I go to (such as Japan, for example) whereas my current 3G phone will. Actually that's a point - would the lack of 3G in the iPhone mean that the SIM/O2 won't allow use of a 3G network when used in another phone? Anyone actually tried this out? Most of my issues with the iPhone kind of disappear if I have the option of keeping my current phone as a backup when travelling.