You Can Still Trial iOS 8.4.1
Apple is still signing off on iOS 8.4. This means that the loophole that allows iOS 8.4.1 users to drop back down to iOS 8.4 remains open.
What this means is that you can download the iPhone 5 iOS 8.4.1 update, try it out, and drop back down to iOS 8.4 if you don't like how it's performing. If you're coming from something older, note that you won't be able to move back down to anything older than iOS 8.4.
It's not clear how long Apple will keep signing off on iOS 8.4.1. It usually lasts for one to two weeks and it could come at any time so you'll need to move fast.