iOS 8.1.1, iPhone 4S, and iPad 2: A little faster, kind of, sometimes
It would be a stretch to say that iOS 7.1 made the iPhone 4 feel fast, but the update improved the phone's performance as much as could reasonably be expected for then-three-and-a-half-year-old hardware. It took what had been a disappointing update and made it usable.
Jump ahead to iOS 8, an update which did pretty much the same thing to the iPhone 4S, the iPad 2, and other hardware based on Apple's aging A5 chip. App launch times slowed. Animations got choppy. Performance became inconsistent. It was the update that made them stop feeling "fast enough," which makes Apple's decision to keep selling the first-gen iPad Mini all the more confusing.
iOS 8.1.1 came out on Monday, promising an iOS 7.1-style update for older devices like the iPhone 4S, iPad 2, iPad Mini, and first-generation iPod Touch. We're here to dispel those notions. iOS 8.1.1 improves performance in a few specific places, ones that may well be important to heavy users. However, it doesn't improve responsiveness or consistency, two of the problems you'll notice the most if you upgrade from iOS 7. Let's look at the short list of things you can expect to improve if you're using an older iDevice and the longer list of things that won't.