I've got it on my daily driver 6S Plus. I like it, it works, so do all my app's that I use all the time. For a major release and a beta 1 it is very good imho. BUT - from advice I read on here and it saved me, turn off automatic iCloud backup's on the phone, as once you backup to iOS 12, you cannot then backup to iOS 11 should you downgrade iOS back. I have done this before. For my daily driver phone, I have found no issues with it. However as you've posted this thread, you clearly have doubts about it.