I’ve been using it on iPad Pro and iPhone 7+ since public beta 3. It’s come a long way since then. I have to say it’s a really great update for the iPad, but the iPhone needs some getting used to. I’m largely comfortable with most of the changes now, including aesthetic, but I can understand if people find iOS 11 polarising. It’s almost as big a leap as iOS 7 was when skeuomorphism went away.
I use a MacBook Pro and iPad Pro at work, usually about 60/40% with the iPad being the 60%. iOS 11 has hugely improved my workflow. The dock and drag/drop is a welcome feature after so long of neutered multitasking. The app switcher including Control Centre is a huge improvement. All in all the iPad Pro has super smooth performance too.
Now all they need to do is reintroduce the force-touch app switcher on the iPhone and I’ll be very happy with it all.