iOS 7 runs like ass on my 4S. I'm forced to get the 5S because I use my phone all day, everyday for work. I don't need to deal with a laggy POS.
My parents love their iPhones. They're older and there's no denying that iPhones are very easy to use which is why I bought them. They updated to the "cool new software" everyone has been talking about. They both have an iPhone 4. iOS 7 literally made those phones unusable. For almost everything you do, there is about a 3 second delay. Opening apps, closing apps, delay in typing, etc.
I'm not exactly thrilled that I have to go to Apple and drop a grand to get new phones. But I'll comment on iOS 7 when I have a device that can actually run it.
2008 TIAG E92 335i 6MT
Mods: Tinted Windows (35%), Aero Lip and JB3...for now