So I had the battery plummet last night, 8 hours and my phone woke me up saying the battery was low. I've been getting 18-19 hrs use, about 5-6 hours of screen on and I had 20 mins of screen on. I live in a LTE area and I generally have good signal. The only thing I had changed was getting an Otterbox Commander case and turning pin lock on. While my screen was black all night, my phone was waking us about 20-25 times during the night, according to battery history. My mobile network bar in battery history was a tan color. I took my case off and it has gone to yellow and green at times. AT&T is sending me a new battery, I reported this to Samsung. I only had the phone for a week before JB came out but I'm still wondering if it has anything to do with JB. I'm really thinking about trading my phone in and just sticking with ICS.
Did you look at your battery usage to see if it was a constant drain or if the plummet got triggered at a specific point? The waking isn't really a problem. All the polling you have set for email, facebook, updates, etc. will wake the phone up every few minutes.
I am intrigued by your comment about changing to PIN lock, though. My phone did not suffer from the plummet for the first few months, then suddenly started (it started with ICS, so it's not isolated to JB). Originally, I had used the Pattern Lock, but then at some point switched to PIN. I don't remember when that was or if it coincides with when the plummet started, but it's an interesting thing to test.
Unfortunately (not really unfortunate), I'm off of work until January 2, so I can't test it until then. But when I get back to work in January, I'll try switching back to Pattern Lock and see if there's any change. That would be weird if it was part of the equation, but I'm willing to try anything.
In the meantime, over the last two weeks, I've gone back and forth with restarting the phone as I'm walking into the office. The plummet happened twice, both times were days when I did not restart the phone in the morning. So I've gotten at least some relief by restarting the phone each morning (once I get into an LTE area).