iOS Improvements Across The Board, For Your Device.
iOS 11 is a free update to Apple's long-running iOS operating system for phones and tablets. A lot of the best features are unique to iPad, from split-screen multitasking with dragging and dropping to a new and improved Dock. iPhone gets a more modest feature boost that it shares with iPad, including improved search suggestions and a modified keyboard.
Can You Handle The Power?
All of iOS 11's new features are fairly well-considered and make for a much better tablet experience, and there's little reason for iPhone users who can update to not do so. iPad Pro users in particular will enjoy a bevy of features that make using the tablet pen both speedier and more flexible. However, it bears noting that the iPhone 5 and 5C are not compatible with iOS 11, and while they'll still be functional, they won't be moving past iOS 10. Additionally, some older iPad models will not be able to handle the new split-screen multitasking feature.
An Easy Upgrade
Unless you've got a tablet or phone that can't run iOS 11, it's worth upgrading, plain and simple. If your tablet or phone is from 2014 or earlier, it might be worth waiting to see if iOS 11 will slow it down noticeably, as happened in some cases with iOS 10. Otherwise, the new features Apple has on offer here are too good for any user to pass up.