I’ve been using iOS 11 on my iPad Pro since I got my new 12.9” model, but I held off installing it on my iPhone until last week. I absolutely rely on my phone when I am in the field at work, and couldn’t afford outages, crashes, or widespread app incompatibility. I waited until I was sure that none of those issues would drag me down, and I’m glad that I did. I’ve had a good experience with 11 on my phone, so far.
iOS 11 is a far bigger and more wide-reaching upgrade on the iPad than the iPhone, so not too much jumped out at me at first beyond the new Control Center. However, once I started using it, the App Store quickly became the most notable difference for me between iOS 10 and 11 on the small screen. While I had looked through the App Store a bit on my iPad and updated my apps, I really didn’t notice how big a difference the new design made until I started using it on the iPhone, with its single-column layout.