If you have an iPhone 4S and are planning to upgrade to iOS 8, then you might want to rethink your decision at this time.
Arstechnica have conducted real-word performance tests on the iPhone 4S running iOS 8. Here are there results when compared to iOS 7.1.2.
As you can see, iOS 8 performs significantly slower when performing common tasks such as opening apps. In the test, Safari took almost twice as long to open (2.16 seconds in iOS 8 as opposed to 1.25 seconds in iOS 7). Other noticeable delays include rebooting your phone, which takes more than 3 seconds more on iOS 8 when compared to iOS 7. Although rebooting your iPhone is not a common task, it’s definitely something to consider before you upgrade.
iOS 8 on an iPhone 4S also misses out on some new features introduced by iOS 8 on newer-gen devices. AirDrop and Handoff are to name two. But it does also gain many new features introduced by iOS 8 that are supported by the iPhone 4S.
Apple usually introduce software updates/bug fixes to new iOS releases which optimises performance on older devices such as the iPhone 4S in this example. Should you be satisfied with the performance of your iPhone 4S on iOS 7, you may want to hold off updating to iOS 8 for now until such updates become available.
Having said that, after iOS 8 releases shortly, you will have up to a couple of days before you will be unable to downgrade back to iOS 7. So in the same breath, it may be better to try it now, and downgrade in the next day or two if you don’t like it. We will have downgrade instructions available soon.
While it may not be completely detrimental to upgrade to iOS 8 now, it is wise to be consider the performance implications on your device before jumping the gun and upgrading.