Finally took the risk and installed 9.3b2 on my 5S.
It's so much different from my first attempt at iOS9 initial release.
This is coming from a huge skeptic and someone very sensitive to FPS. I have also updated from iOS8.4.1, so it's a very good comparison for me, and to be honest it seems as fast (some apps actually feel faster to open, like the camera seems to open and be active instantly).
CC has no lag, except on the screen where the clock is located it seems a tiny bit jittery (then again, iOS8.4.1 had some CC jitter), and nor does the NC.
Very happy - only bug I found is if I have notifications on the lock screen, unlocking causes this weird slide up animation and the clock doesn't appear immediately - I don't really see the point in this, but it sort of makes sense since the notifications slide out of view...
Also, having the iTunes Store hidden via Restrictions hides the App Store settings from the main settings menu completely (this didn't happen before, and it was nice to be able to hide the iTunes Store...).
Very happy so far - I am sure 9.3 final will be even better, and I'm glad given I really want the F.Lux feature.
I can also confirm - hiding the Clock app into a folder solves CC and NC lag on the page the Clock app is located, unlock stutter, as well as swiping lag between home screens, and app switcher lag (to some extent). So yeah.... screw the animated Clock app!