I've had two cases lately where my N800 was dead in the morning because the battery ran out. This is unfortunate because it reduces the battery capacity. Fortunately though it's not disastrous like when my PDAs run out of battery, as nothing is lost (the PDAs are basically scratched). I'm not sure of the cause though. But I noticed that the first time load-applet-run indicated CPU usage in the evening, unfortunately I hadn't yet learned that it was a CPU bar I was watching. Don't know what was running. What I've done since the second incident is:
a) I disabled the meta crawler. I can't see that I need it for anything, and I haven't seen any side effects of disabling it either.
b) Every evening I look at load-applet-run to verify that the CPU bar is all clear, if it's not completely white I check what's running, if I can't figure it out I'll reboot. Anyway I haven't had another incident yet after a). That doesn't mean the metacrawler is to blame though, it could be coincidence. However, I didn't have any such unexplained battery drainage overnight in the previous firmware versions. Could still be a coincidence though.

Unfortunately, after those two battery discharges the capacity has definitely got a dent, this has also been the case with every other lithium-powered device I own where the battery was fully discharged. Avoid discharging a lithium battery at all costs, I wouldn't even do the initial discharge-and-charge cycle so often recommended to new users.