I have discovered a problem with a particular wi-fi router only: When connected to this one my N800 sucks battery like there's no tomorrow. It _only_ happens with this router (which is one I own), it's never happened with any other access point anywhere. It took a while before I realised what's happening. Presumably the router somehow prevents my N800 from going into wi-fi sleep mode or something.

I don't have the exact details of this router (it's not located here), but it's a SiS chipset based one. I'll look for firmware upgrades for it and do some more testing if so.