What a difference a card makes.
One of the first things I installed after flashing my N800 to 5.2008.43-7 was Advanced Power Applet, and used it to verify that I was still getting the terrible battery drain. (as other people got, about 3% per hour) both when booting from SD and from flash.

Based on the idea that it may be the SD card(s) I tried booting to flash in different configs, waiting for it to settle, and then measuring after an hour. This was informal, I didn't have to patience to be methodical, but my results are clear anyway:

16GB A-data Class 6 : 3%/hour
2GB Kingston : 1.8%/hour
16GB Patriot Class 6 : .6%/hour!

So I have swapped 16GB cards from my N800 and my camera (Nikon D40x - which I hope has different power management) and suddenly I have the battery life I had before upgrading to Diablo - which was the same moment I started using that A-data 16GB card, I should have tried this before, but didn't think cheap cards differed.

In the 9 hours since performing the switch and topping it off (which is 94.5% according to adv. power) it has only lost 4.5% - and this is booting from that Patriot card, with a microB and an Xterm open but no wi-fi (to simulate being left in a pocket after use)

This also happed to fix another problem I have been having since then.

So, I have a simple question: Why does a card that isn't being read or written to still use any power? (no swap, metalayer-crawler, etc. were involved in the boot from flash test that still used 3%/hour with the A-data)