I'm assuming everyone is sending in their bug reports using the Feedback Assistant, right? And not just complaining about the (legitimate) problems on forums, or downgrading back to iOS 8? That's the point of beta testing.
8.4.1 is much more stable... but, I mean... it should be. 9 is still on a beta, and (by MY amount of feedback and logs) is at least a couple of versions away from any GM candidate. Still having Home Sharing issues, I'm being inundated with "Please sign in to iCloud" notifications, graphics stuttering and doing their own thing sometimes... and THEN some of the same drastic battery issues - though only on my iPad, and only since the last 2 beta builds.
All of that, and me still not quite understanding the "swipe right" search vs. the "swipe down" search (or necessity of one), or whatever the hell they consider themselves doing with the Music app, and I still say that it should be a worthwile upgrade when it's all said and done.
REPORT THOSE BUGS AND ISSUES.
(Seeing immediate performance gains with the El Cap beta on my Macs; iOS 9, much less)