I've had an iPhone 4S for a few weeks now. It's unusual for me to get a new phone this soon after its launch. I took the plunge this time mainly in order to diversify my development devices. I plan to keep my old 4 on iOS 4.3 for compatibility testing and use the 4S as my main dev device — as well as my everyday phone.
There's not really much left for me to say about the 4S which other people haven't already said. Like Marco Arment, I can't say I've really noticed much of a speed improvement. This probably says a lot about the power of the iPhone 4. Certainly on paper the 4S should be noticeably faster. I usually shy away from having the fastest device available as my day-to-day development device from a — more than likely misplaced — feeling that by not having to worry about performance I end up writing inefficient code. I guess it's hard to shake my assembly language roots.
I must admit that I haven't got much use out of Siri so far. We had fun with it — I'd love to say 'she', but over here they've made Siri a bloke — over lunch one time, but that's about it. I guess I just feel too self-conscious talking to my phone.
And the only other new stand-out feature of the 4S over the 4 is the rattle somewhere at the top of the device near the mute switch. But I'm not sure that's a standard feature.
