ok, I've done some playing with a couple of suggestions given on a number of forums.
I usually have Reduce Motion turned on, and after the update both my iPad Air and iPhone5s heated up, and battery drain was huge.
Im not sure where I read it, but someone suggested to turn on Reduce Motion, to reduce a process which was running a lot of process cycles - if it's already on, turn it off and on again in Settings/General/Accessibility (in true IT Crowd Style)
So my method what to do this first on the iPad Air (wifi/cell/32gb)
Before I updated I
Turned "Off" Reduce Motion in Setting/General/Accessibility
Updated to iOS9pb3
It heated up again.
I then Turned "On" Reduce Motion.
Battery seems a lot better, iPad is not hot.
I ran it for a couple of days - battery drain was acceptable.
I did this on the iPhone5c last night too, and again iphone is cooler (but still a tiny bit warm to touch, 20'c methinks), and the battery drain is again acceptable.
I have yet to try low-power mode, which I've been told makes it even better.
I will report back after the weekend with comments.