Keep in mind that the battery count will only reset once the iPad has reached a full charge (sometimes if you pull the cord out when it hasn't been at 100% for long it does not reset) and it seems to add usage time to the standby time. (so 10 hours used = +10 hours standby)
I'm not sure if playing audio in the background when sleeping counts as usage time, or standby time either.
I have definitely noticed an extra couple of hours battery life out of iOS 6, as they seem to have fixed whatever bugs were causing idle CPU usage to gradually rise on iOS 5. (my iPad 2 & 3 would gradually increase to about 20% idle CPU usage over the course of a week until they were reset a couple of times)
I do regularly get something in the region of 10-12 hours though, and more if I'm at low brightness for most of my usage. At lower brightness, I get better battery life out of the iPad 3 than the iPad 2, at high brightness, I get better usage out of my iPad 2. (but not by much, maybe an hour)