I don't know what the aim of the tablets is. I only know what I need and what I'm willing to spend money on: a tiny laptop-replacement.

Sometimes I feel there's not only a languages barrier here... It really feels we have two incompatible types of brains. I may understand your words, but I don't understand the way you think so it's difficult for me to answer.

What fails? We have desktop apps on the NITs and they work perfectly. I don't see the desktop paradigm failing.

I have to admit I don't consider myself a general user. I made the experience that what I want is usually a niche product. Actually, I was prepared for the 770 to be a one time only so I'm still somewhat surprised the did the N800 and the N810...

Anyway: My job is not to do market research about the general user (I couldn't care less). Also, I don't think there such a thing as "the point of mobile devices." - I carry several kinds of mobile devices, and I would be very upset if my tablet would be like my phone or my phone would be like my music player. (And I guess my mother would be more than upset if her phone would be like mine...)
There's a point in simplicity when you want it. And there's a point in a rich UI when you need it.

(One more thing about the "general user": It's the market everybody fights for. It might be a wise business decision to concentrate on a few niche markets, too, as long as they're not too small.)

Right, mobile apps can complement the desktop apps in function and extend it that way. That's what I'd expect on my mobile phone.
Then, as an additional device, I have my music player because although my cell phone does play music files, in many situations it's too big as a music player.
And, as a third device, I want a portable computer. I would have a laptop, but it's too big for me. Therefore I chose the 770, now the N800. And the applications on my mobile phone can still complement the desktop applications on my N800-computer.......

Oh, and: The concept might in fact be doomed in a way, at least in the Maemo context. Nokia threatens to introduce a "finger friendly" UI with Maemo 5, which probably means wasted screen estate, less effective UI (more clicks to achieve the same result), less accuracy... This could in fact make it much harder to do anything useful with the tablet.

But until then we'll have quite a lot of alternatives out there and I expect smart people to make it even easier than now to run alternative OSs (like there's Debian etc. already) on both the Nokia tablets and other devices. So in a way, whatever Nokia does to the Maemo UI, as long as they allow people to choose a different OS that better suits my need, I'm fine.

EDIT: One more thing: Even if I'll be using some other OS instead of Maemo 5 - if Nokia really pushes and supports all these upstream projects, chances are that I'll be using most of the core technologies that make people excited about Maemo 5 in, say, Debian on the N900 or in Ubuntu Mobile on whatever esoteric hardware I'll buy. Isn't this world beautiful?