Yeah, I noticed my 6.1 iPad hasn't backed up since my JB. I tried manually doing it, it fails. Tried deleting the last icloud backup for the pad in case that was causing the issue, didn't help.
On the other hand, my 6.1 iPhone is backing up to icloud OK.
OoooK, it made me a liar. It hadn't worked the few times I tried it. I did a little searching and some people were saying to look at PKGbackup. I fired up the app on both devices, decided to back them both up again. Tried icloud backup on the phone, worked. Tried icloud backup on the ipad, and this time it worked. SHRUG.