Okay, I'm fairly sure now that Firefox is the culprit behind the sudden battery drain.

Recap: after the update I reinstalled my applications, including Firefox. Then I noticed that the battery drained completely within only a few hours. I uninstalled a few apps, including Firefox, and the problem seemed to go away. Then I began troubleshooting by reinstalling the apps one by one, starting with Firefox.

Sure enough, after installing Firefox the battery dropped again, drastically. From having been fully charged I suddenly noticed it being almost empty. I then checked with the top command and noticed hildon-home using around 20% CPU constantly. I uninstalled Firefox again, and after a reboot and some waiting, the battery became stable again. I've had it like that for many hours now without noticeable drain.

So: UNINSTALL FIREFOX! It somehow makes hildon-home go into overdrive and eat your battery in a few hours time. Make sure you get the Mozilla runtimes too. Simply not using FF doesn't help, you gotta uninstall it.

Hope this helps anyone else having battery troubles after the update!