All the various UI downgrades aside (wasted screen space for less icons available in things like the shortcut tray or the more taps before you can actually type a number in the phone menu), one really annoying issue i'm having is that my system alarms cause my lock screen to effectively have a siezure when it goes off - the top bar blinks wildly, the main lock screen blinks wildy, the home button nav bar at the bottom blinks wildly as if its all fading in and out desynchronised from each other. I can't inertact with it at all and my only option is the force reboot the phone. Generally the whole update is quite terrible and I wish i could easily just go back.