Afair a year ago Sebastian said something about Testing. It would also be the logical choice as it kind of balances the need for quick development that a new device needs with the relative ease some users might need to handle it.

Sort of. It's still Arm. So it would be as "normal" as Debian/armhf can get.
This basically means a light desktop like LXDE, Xfce or some WM of your choice without HW acceleration (so certainly no Gnome) and some software that's missing in the arm ports (e.g. Chromium).
We might even be able to borrow some software from the PYRA or RPi repos. So don't count Chromium out completely yet, if that matters to you.

Yes.

Easy Debian has to struggle with some additional limitations, the biggest being (not sorted):
1. low RAM for Debian ON TOP of Maemo
2. Maemo's outdated foundation (running Jessie on Kernel 2.6.28 is like building an F1 car on a 2CV chassis)
3. my incompetence

None of that will apply to Debian on the Neo900. If you want to get a better impression on how it could run, try DebiaN900 [1] on your N900 and multiply the performance by a factor of 1.5 (that is as long as your N900 RAM is not full). It's roughly on par with a fast Pentium II running a current Debian. You'll have to stick with lightweight software, but if you do that you should be able to reach a decent performance for simple office tasks.

You'll notice some other problems in DebiaN900 however:
1. No phone support.
2. Very poor battery runtime for a mobile device (6h idle).

I think the phone issue will get sorted out, if the existing problems of the fso suite in Debian can be solved. Shortly before the Jessie release it didn't play well with Systemd I think.
The battery problem might be no problem on the Neo900 at all. Everything we need is a kernel that supports S2RAM.


[1] http://talk.maemo.org/showthread.php?t=93878