Well, first and most important, the lack of a hard cover. The 770 lives in my backpack most of the time, with books, shoes, cell phones, cameras and other stuff being thrown in and tossed around. I feel comfortable doing this because nothing can harm my 770 in there. A N800 would have serious scratches on the display meanwhile. (Probably it would even be broken by now.)

(The tablets being sold as "mobile devices", I can not understand what made Nokia drop the hard cover; I know 2 N800-users now, none of them ever takes the device with them. They leave it at home.)

Another point was the the keys (zoom, d-pad, etc.). Especially the ones on the top are terribly small and hard to press on an N800. (The N810 seems to have a better design here.) But even the keys on the front, although big enough, have a cheap feeling to them.

Size. The 770 is so small and light!

Then, there's of course the looks. I'm not the Apple-type of customer, so looks isnt all that matters to me, but compared to the elegance of the black 770, the N800 looked like a toy.