I have done extensive troubleshooting and I personally believe it's the jailbreak, but saying that on this site you may as well have committed murder!
Couldn't agree more. I restored, jailbroke, and installed NO cydia tweaks.
For some reason, when the iPad is "asleep", it drains almost nothing, maybe 2% overnight. But as soon as I wake it up and start using it, it goes down about 10% in 30 minutes. And that's without changing my habits at all from before the jailbreak.
For example, I was at a seminar about a month ago (before jailbreak), and took handwritten notes in Noteshelf. At the end of about 8 hours of constant use (with an hour intermission in the beginning), it was down to 70%, which was astounding.
Recently, after jailbreaking, I wrote notes using the same app, with nothing in the background, the brightness set at the same level I always have it at, no Cydia tweaks installed, and it went down to 50% in about 3 hours.
I don't care what anyone says. This jailbreak does terrible things to the battery. I don't believe it affects everyone the same, but it's the culprit. There is no other explanation.
It's not too surprising. I don't know if anyone has an android device, but in the rooting community it's very common to see some install the exact same kernel or ROM as someone else, on the same phone, and have vastly different battery experiences.
Every device is the same, but every device also isn't, if you get my meaning.