Please use the (Quote) Button! It would be much easier to read your comments that way.

... which drives me nuts.

• Battery life is nice, but: My S60 cellphone can do many of the things the tablet does for me (and there's more software) and has a much better battery life.
• Touch screen: I don't get this one. We both know there are a lot of devices with touch screens around.
• UMPCs: You almost got me. If Nokia didn't have the tablets, I'd probably have bought a UMPC. It's almost the same concept, only too big and too heavy. I will seriously look at Moblin-based devices though as they become mature.

UI for me is the UI of the application on the screen; I probably don't even think of the D-pad etc. because in my world, applications don't know if they happen to run on a Nokia tablet, on a Moblin-based device or on my desktop. So the UI is what the application draws on the screen, not what (more or less by chance) is in the hardware.
There are only very few applications that rely on the hardware buttons you mention (I think Vagalume does for volume); usually they're only an additional way to do something that can well be done on the touch screen in some menu.

Again, as with your statement above about the touch screen, I don't understand what you're saying here. My own private definition of a desktop-like experience is: A start menu, applications that run side by side and show their icons in the status bar so that I can easily switch, a number of small status icons, a unix-type file system, the possibility to install and uninstall applications (or write my own if only I could), windows, application menus, dialogs, buttons, drop down menus, checkboxes...
All of this is there on my N800. And it's even faster than the 90Mhz Pentium with 192MB of RAM I use at weekends.
The only thing missing are a few expansion slots for network-, sound- or graphic-cards. I hope the N900 will... no.

I don't see how any application would need to "support" a touch screen. Applications support clicks (or rather: listen to such events), and the touch screen is one way to produce them (as is the touchpad on a laptop, which applications don't "support").

I'm not quite sure what your idea of "leveraging" is in this context. My opinion is that it should be enough in most cases to hildonize the beast. There are applications that will need more attention UI-wise: you know, the one gigantic options dialog that's twice as high as the screen might look better when split into 3 tabs etc. - But that's cosmetics and fine tuning. In general, I feel more comfortable when an application looks the same on my tablet as it does on my desktop. I use the same applications with the same settings on all my computers. Why should the tablet be different?