When I first got my HTC One X, I was very happy with the battery life. I've gotten 4 days out of it a couple times (obviously not much happened those days).
Now, I'm enjoying the same pain many here have.
Since it seems the problem surfaces during the night, I'm going to use an awesome app to combat it: Tasker. It can take any event and cause any other event. I have it set now so that the phone goes into airplane mode from 12am to 6am.
We'll see how it goes.
Kurt
12/6 Update: I've got plenty of battery this morning

12/13 Update: Still haven't had the problem return. My battery has slowly recovered to the normal 3 day usage.
12/31 Update: Well, after over 3 full weeks of bliss, it happened to me this morning after 9 am. Bummer.
1/21 Update: My 12/31 instant drain only happened once. I do recommend "Tasker" for anyone that suffers from nightly drains.
I should also note I disabled all facebook, friendstream, and twitter apps on 12/5. So, could be one of those apps were causing my problem.