iOS 9 on the iPhone 4S
Our recommendation for iPhone 4S users is pretty much the same one we gave to iPad 2 users earlier today: if you’re running iOS 8, go ahead and upgrade. The small screen is frustrating, but performance is about the same, and for all the stuff you’re missing you’re still getting a whole bunch of the new features we highlighted in our iOS 9 review. It’s got the better, more legible software keyboard, the upgraded first-party apps, and more.
If you’re still running iOS 7, at this point we’d say you should probably upgrade, not because you won’t take a small performance hit, but because developers will increasingly abandon that older OS version if they haven’t already. Apple’s iOS updates roll out quickly, but the downside of that is that there’s not a ton of incentive for developers to support older releases forever and ever. It’s common for developers to support the current release and the immediately previous release, but starting today that doesn’t cover iOS 7 anymore. And though it’s not going to make your old device feel new again, iOS 9 is probably Apple’s best, most stable x.0 iOS release in years.
Apple might surprise us again next year, but this is probably the end of the line for the iPhone 4S. The iPhone 6S is brand new, and if you want a smaller phone that’s still a lot faster, the iPhone 5S is cheaper than it’s ever been. iOS 9 on the 4S is still perfectly good for a backup phone or a hand-me-down to a less demanding member of the family, but if you use your smartphone heavily you’d be served well by an upgrade at this point.