I have two iPads, both upgraded to IOS 9.02. I can't use iCloud on either pad because I can't change the iCloud Apple ID. Here's why:
I changed the Email address of my Apple ID primary account since the old one was at my previous employer and is no longer accessible. I made this change at Apple.com.
On both pads, I had no problem changing the App and iTunes store apple ID. I can download Apps and make purchases on both pads.
When I try to change Settings|iCloud it asks me to
Sign in to iCloud for
Apple ID "firstname.lastname@example.org".
Attempting to sign out brings up:
Enter the Apple ID for the "email@example.com" to turn off Find My iPad.
No password is acceptable here. I cannot change the Apple ID back to since I cannot verify the email and the change doesn't take effect until verification has been completed. I have tried changing back to the old ID get a
Account is Locked
message on the iPad when I try to use it - probably because of the unverified address.
Apple's 'community' has been less than helpful, filled with people saying to go to the useless Apple iForgot and other such nonsense. It would appear that others just got sick of the whole thing and quit trying.