Matt Birchler at BirchTree about reasons not to install iOS 11 beta:
You shouldn’t install the iOS 11 beta for many reasons, most notably the fact that tons of things are just plain broken. Here’s a selection of things that are broken or annoying in the current beta state.
I never install beta versions of iOS and macOS on my iPhone and Macs. These devices are too important to me to take the risk and get buggy software. I admit than I’m very curious about APFS but not that much that I would install High Sierra beta (the public version is not out yet).