Other than a few issues surrounding the new Music app and service, I've heard nothing negative about the iOS 8.4 update. Even those are minor, if you avoid turning on the iCloud Music Library; which is entirely optional.
iOS 8.4 introduced nothing new in the way of power or battery management. Mostly it got the new Music app, the new Apple Music service (opt in for a free three month trial), moving audiobooks to iBooks, and some bug fixes. Oh, and a few security updates, at least one considered serious.
While there is never a guarantee that something new will not pop up, there is little reason to expect it in this case.
Then again, unless you want to try try the new Apple Music service while the free trial is going on there is nothing about the update that demands immediate adoption.