My iPad nags me to update to iOS 10 every day. I won't allow it (even though it has already downloaded). I will let them get to version 10.1 at the very earliest before allowing it, precisely because Apple has got so sloppy over the past few years with issues like this.
Missus has an iPhone 5s which is absolutely killing its battery since the upgrade (which I forgot to tell her not to do). It also developed a tendency to deregister itself with our service provider and had to be rebooted a couple of times.
Sorry I know none of that helps you but it's worth bearing in mind for future. Never download the first version of anything.