I decided to update to iOS9 last week - after running some test on older divices and friend's devices that were allready on iOS9
tests showed that our main FMGo app was slower in some aspects - but I did not feel uncomfortable. My iPad4 was too slow, the current Air2 was OK
after working for some days under iOS9, I can only recommend to stay on 8..
- sloooooooow, even on the air2, some tasks are too slow
- mistipps, sometimes, the 'airdrop part' appears on the bottom
- when 'auto correct' (words in the bar over the keyboard)' sometimes a wrong selection appears - and will be replaced
- every now and then, the cursor can't be placed using the finger (safari as well)
- split view... seems the or one of the culprits. Windows in FM does no longer fit, has to moved around
it's nit just FileMaker...
- iPhone 5s: Sometimes , one can not establish the loudspeeker, sometimes vice versa
- iPhone 5s: Camera from lock screen will appear, the button doesn't work (not every time)
concerning speed, I will activate the speed-check CF's for checking. But it's the very same app that did run fine under iOS8 (well... after 14.02 came out..)