try calibrating your battery.
1. drain your battery to the point that your iPad turns off automatically (0%) then
2. let your iPad charge without using it.
Already done that, also did a clean restore...still the same.
When you did the clean install, did you restore your iPad from a Back-up or did you set it up as a new device?
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8G4 Safari/6533.18.5)
Of course it's not normal. I don't have an iPad (yet) but I can surely tell you that 91% isn't fully charged. You either have a software issue (reboot/restore) or a lemon (return to place of purchase).
Yep, you're right. 91% is not a full recharge in anyone's book.
Does it say "Fully Charged" or does it just say 91% with a picture of a full battery?
I would suggest returning it since it is not normal. If it didn't change after calibrating it most likely is faulty battery. Just take it to apple genius bar and they should take care of you they should have some stock for replacements.