I love certain functionality. The control centre thingie that you can swipe up from the bottom of the screen. I use Do Not Disturb, change Brightness and use the Timer so often, it's great to have easier access to it. I also love that the timer now shows on the lock screen. Paging for groups of apps is good too, although I wish I could display more on one page by making the icons smaller.
Stuff I don't like but can live with:
-The fact that instead of looking like I'm a professional with a phone, I now look like a teenager due to the new button styles, colours etc
-In the camera app it's not very clear when you've taken a picture. I took 6 pictures of the same thing the other day, thinking I'd only taken 2, because the visual cue to show you that your picture has been taken is not very noticeable.
Stuff I absolutely LOATHE:
-Calendar. You can no longer see a short summary of your day while having the rest of the calendar in view. You have to go to a specific date, then you see the WHOLE day, even times you have no appointments for, so you end up scrolling up and down to find the appointment you have. It completely lacks overview.
-When you press the home button to activate the screen you see the time & date big on the screen as usual. BUT if you're playing music, you don't see the time big (it's small at the top of the screen) and it doesn't display the date at all.
There's probably more but I can't think of it. I've only been an iPhone user for a year (the iPhone 5 was my first smartphone! I am from the stone ages indeed) and I used to love it. But this new iOS has made me think of looking into an Android device.