OK, I got my problem figured out. And, I wasn't imagining things 🙂
Looking at the battery log file while the device was in standby, it was full of these events:
05/18/12 02:25:51 [Battery] level=88.80%
<snip>
05/18/12 02:26:30 [Assertion] id=0x17_0x12d02ac; state=released; process=SpringBoard; pid=23; name=com.apple.persistentconnection[SpringBoard,23,com.spoonjuice.nightstandhd- PendingTimer(f103170)]; type=PreventUserIdleSystemSleep; level=255; timeout_type=turn_off; timeout=90; held_for=00:00:29;
05/18/12 02:26:30 [Assertion] id=0x17_0x12d02b2; state=created; process=SpringBoard; pid=23; name=com.apple.persistentconnection[SpringBoard,23,com.spoonjuice.nightstandhd- PendingTimer(10bedca0)]; type=PreventUserIdleSystemSleep; level=255; timeout_type=turn_off; timeout=90; held_for=00:00:00;
<snip>
05/18/12 03:24:35 [Battery] level=88.02%;
I originally said 1% per hour, and it's actually a little less than that. The interesting thing is, I never even used nightstand-hd on this ipad -- it was a restore from a previous ipad 2 backup (and I never regularly used the app there, either), so perhaps there was some strangeness in the restore. (I do understand why preventing sleep while on power would be desireable for an app like this.) I uninstalled it, and tested -- battery level was not run down any more -- I reinstalled and used the app, and still battery level was not run down, either.
Of course, there is normal activity in there -- push notifications, etc. -- but this was definitely the culprit, as these were repeated over and over every 30 seconds or so.
