Most of the changes are cosmetic, which doesn't strike me as overly interesting, though needed. However, I like the Control Center. That will not only let you access your most-used system features, but will allow you to do so from any screen, but just swiping up from the bottom of a screen. Also, the "voice-assistant" feature known as Siri now will let you manage many system changes, like turning on Bluetooth.
There is also a flashlight feature, something previously only available through third-party apps. iTunes Radio expands iTunes to include favorite stations. And iOS now will allow for automatic updates of your apps (though exactly how this will work, I'm not sure...)