For me, someone born in the mid-60s, it is just astounding technology. As a child I expected a future of jet packs, space travel, flying cars, cures for cancer etc etc. None of that happened, but we got a device that makes a Star Trek communicator look like a total piece of crap in comparison. The iPhone, and even more so in its shiny new buttonless X guise, represents that future. A computer far more powerful than any mainframe even the US military had in the 1980s that operates via touch, voice control, has GPS, a pro-grade digicam, arcade-quality gaming built in along with the ability to hold about a month's worth of lossless music and even has a telephone built in. Add to that the best mobile apps on the planet for whatever your interests, so you can use it from anything from an analogue synthesiser (a proper Moog, Korg etc) to a heart monitor. Come on, it is bloody amazing! Alternatively you could buy a fancy interconnect for a hi-fi system for the money!
PS Sure, as ever, there are other smartphones that do some of this stuff, some may do some of it better and dud some of it last year, but what Apple do time and again is to do it better and as a cohesive designed whole. If the best Android phone is £7-800 or so I would so happily pay the extra £200!