I agree with sonoros, I'm happy with my 770. SD-slots of N800 are tempting for movie storage and easy viewing of pictures taken with ixus but it's still not worth 400€. Well 770 still sells for 200€ in local eBay, so the upgrade is only half of the price.

Unlike the apocalypse prophets, I expect 770 to get N800 (bora) compatibility soon. Compatibility is just matter of having matching shared libraries as they did not change the toolchain. And almost every shared library on 770 is Open Source.