Obviously there are a number of considerations here. If you want to feel like you saved a lot, probably go with the n810.

But as for me, I'll never upgrade from my n800 *unless* the newer model has a D-Pad somewhere on the face plate. The n810 doesn't have this, as its D-Pad is on the slide-out keyboard.

Ever since screen rotation was introduced for OS2008, the vast majority of time spent with my NIT has been reading blogs (with bloglines+skweezer) and news in portrait mode (also, reading gmail in portrait mode with iphone spoof is delightful; so is google reader mobile for iphone, if you use that). With the n800's D-Pad at the bottom of the tablet when in portrait mode, i can hold the tablet in my left hand and navigate down the news story with my left thumb. (In fact, this is ergonomically easier if you do *not* remap the D-Pad so that landscape's left button is portrait's down button.)

For me--again, this is just a personal preference--this is much better than having to scroll by touching the screen, whether it be with the stylus or with a finger, as you would have to do (right?)with the n810.

oh, and....you'll need this to change default d-pad link scrolling to page scrolling.