My iPhone seems no better nor worse (performance-wise) with iOS 7. Or, if you will, it works as expected.
Which offers a conundrum - with my 3 year wireless plan coming to an end at the beginning of the year, do I stick with my current provider and my old phone, or consider a move on both fronts? Normally, I'd be considering a hardware upgrade (because, if the old phone does die, it'll mean revisiting the whole plan), but frankly, I see nothing 'insanely great' in the current crop of iPhone products - in fact, it's more of the same. And I'm not sure ennui (or the hope that Apple might offer a game-changer in iPhone 6 sometime in 2014) is enough of a reason to stick around.
It wouldn't be up for discussion if Apple offered anywhere near the selection of hardware options that the competition does - but if my iPhone 4 runs fine with the current iOS, why consider any upgrade?