The Canonical approach to Ubuntu Touch (Phone/Tablet) is a surprise but it can work. Pro's :
- more than one hundred devices which run Android/CyanogenMod can be adapted to run Ubuntu Phone/Tablet OS, there is already about additional 20 devices being worked to run Ubuntu Touch;
- so many smartphones/tablets manufacturers can (technically) decide to release devices with Ubuntu Phone/Tablet OS;
- from > 50 thousand Ubuntu packages, almost all of them which don't depend on X11 and desktop GUI (Gtk, Qt4, etc) will run;
- many Qt4/QML softwares can be ported to Qt5/QML, from Maemo 5, MeeGo Harmattan, BlackBerry, Nemo Mobile, Plasma Active, etc;
- for example, 2 thousand Pyhon packages on Ubuntu Touch instead of few hundreds or dozens on Maemo 5 / MeeGo Harmattan / Nemo / Tizen. There is Python 2.4, 2.5, 2.6, 2.7, 3.1, 3.2 and 3.3;

Con's :
- no X11, so "ssh -X" and X11 softwares won't work;
- Python for the moment has no binding to Qt5, i.e., there is no PySide for Qt5. But maybe it will be released in 2013;
- lack of current GUI softwares written in Qt5/QML. I think it will take an year, i.e., until 2014, to have some thousand Qt5/QML softwares on Ubuntu Touch.

I don't understand how Ubuntu Touch will be turned on a Ubuntu desktop if the smartphone/tablet is pluged on TV/monitor, keyboard and mouse. As desktop GUI softwares depend on X11...