Whats it like on the iPad 2? My observations from youtube is that every app will lag when its opened (it goes black and stays on the home screen for longer than iOS 8.. )
I do not have an iPad 2, so I can't answer your question directly, however I can confirm this is an issue in general (there is a noticeable app launch delay) on the 4s, and also on the 5/5c, and 5s. Seems to be a general iOS 9 beta issue. It could be related to how the beta is collecting diagnostic information, or it could be a bug. I'm not sure - I've been sending apple regular feedback.
Still, the animations are smoother and more responsive - it feels more "fluid" is the best way to put it. Its the most "fluid" the 4s has felt since iOS 7.1.2, to put in another way. Even now if I do a fresh restore to 8.4.1, it feels more laggy and stuttery; more skipped frames and incomplete or delayed animations vs iOS 9 b5/pb3. I do hope that Apple sorts out the app launch delay because that is annoying and one knock against iOS 9 beta right now.
If they can sort that out, along with the keyboard lag that hits the device (4s) randomly, it will be an improvement over iOS 8 I feel.
They already improved the multitask switcher (4s) with the latest build - it is much more fluid than it was in the previous beta and more responsive. Apple did reply to my feedback regarding certain issues that were fixed over the last few beta's so there is hope they are aware of the delay issue and will continue to work on performance.
Still some ironing out to be done on Apple's part, but I can say iOS 9 is looking promising for older devices.
