Barbara has an iPhone 5S that keeps bugging her to install iOS 11. Should she? Leo says if Apple thinks it can run it, then she can run it. Security improvements are a good benefit. Also, some apps may not run without it. But the reviews say it will slow it down. It will still be faster than an iPhone 5 running iOS 10, though. So she should go ahead. It'll be usable. She should check out this article at arstechnica.com.