Even if it does work for some people. Its still technically flawed. First of all getting into the thumboard itself is a pain because sometimes the n800 picks up that your whole finger is there, but most of the time (For me at least) it just assumes your finger is a stylus and brings up the normal keyboard.
When I am in the thumboard and attempt to type with both thumbs, alot of times I can type, but there are many spelling mistakes due to it thinking that I pressed another key instead of the one I intended.
The N810 is a rip off. You are paying twice as much for basically just GPS and a built in keyboard. You lose the dual SD card slots, which is the reason I even got a N800. I have two 8GB SD Cards, and if I were ever to upgrade to the N810 I wouldn't be able to use any of them.