the decision between 800 and 810 depends on what you want from it. I went for an 800 as I wanted as much local storage for music as I could get (2x16GB), and in-car navigation. I have an external bluetooth GPS, which I can also use with my phone and Nokia sports tracker leaving my tablet at home so that works better for me than a built in GPS, and I have a bluetooth kbd for those occasions I need to do some serious typing.
I reckon one thing is certain though once you get one, your 770 will start gathering dust. I pick mine up occasionally and quickly drop it again as I get frustrated with it's slowness and instabilty compared to my N800