What's really pleasing me about iOS 8.3 is the fact the keyboard is more responsive in Safari and most of all the animation when the keyboard slides up from the bottom of the screen in Spotlight is super smooth again, like iOS 7 (this is on iPad Air).
The animation when you quit Spotlight and the blur fades out to reveal the home screen has a tiny bit of stutter near the end, but it's a vast improvement on iOS 8.1.x builds where the keyboard would judder as it slide up from the bottom of the screen. Although oddly, on 8.1.x if you kept your finger on the screen as you slowly slide your finger down, the keyboard came up smoothly.
Now on 8.3 when you just swipe down with one finger, the keyboard appears smoothly again. If they can fix the exit animation stutter it'll be perfect.
In fact I'm finding iOS 8.3 is as close to iOS 7.1.2 performance on iPad Air as iOS 8 has ever been. So smooth throughout the UI, with the exception of the usual Spotlight rotation animation which remains choppy on almost every device