In theory it should work with some limitations. It would need running older 2.6.18 kernel (= back to 330Mhz) and the kernel may need some tweaks to boot (i.e backport 810 board configuration sources). Also initfs may need some changes, battery charging daemon (bme) is different for n800 an n810 (perhaps due to different battery used).

Also there is one major issue - both older kernel and OS2007 does not support builtin keyboard (and other extra HW like GPS or light sensor). Backporting kernel driver should be relatively easy but disabling/enabling on-screen keyboard when HW keyboard is opened or closed may be a bit tricky to do in OS2007.

I think I'll try it when I get 810 but it may not be very usable for normal users who expect all builtin HW to work smoothly.