No iOS 8.4.1 did not run perfectly. Safari on my iPad 2 was barely useable. I'd rather have lag and stutter and useable safari. Thankfully with iOS 9 I don't have to choose .
Safari was intolerable on 8.4.1 (crash/reloads galore), plus the Apple Music lagged the whole system.
If you didn't use Safari or the Apple Music, it was smooth. Like you, I would rather have stability. Having said that, I'm glad they're working on performance in 9.2 b1.