Gerbick's impressions point to what I am thinking.

I believe Nokia has used the tablets N770 - N810 as stepping stones towards a future of Linux pocketables.
Someone from Nokia spoke of steps 1 to 5, N810 beeing nr. 3.

My guess is that Nokia has focused their software development on the future pocket Linux OS,
and used the tablets to communicate with the Linux community.
Of course the tablets had to be useful for consumers, but I guess that Nokia will target more professional use
first with "step 5 (4?)". Nr. 5 = Harmattan ? Or Harmattan+ ?

E.g.:
Surfing on complex websites with many photos is a bit slow, many pro's would want more power before they consider leaving their laptop at home.
In Sweden shops have never had these tablets in stock, although we are rather gadget minded.
You could buy them from web stores, or order them at your dealer, but then he'd expect you to buy.

Consider Nokias strategy of (heavily) bying into supporting development, and at the same time preparing a continuation of Symbian more independant of Nokia.