I'd recommend to use Qt and just start with it.
You'll be surprised how much of your code can be reused across different platforms.
By the way, I develop my "N900 Qt applications" as "common Linux Qt applications" using Qt Creator and then essentially only "recompile" these for the N900 in scratchbox.
Of course, you have to keep limitations like the small screen size in mind in order for your applications being actually usable on the N900 (but my guess is that this will be the same for mobile MeeGo devices ).
Though, for most simple applications the whole process is really straight forward.

Edit:
Developing for "different platforms" with Qt not only means developing for Maemo and Meego but also for other "common/desktop" Linux Distributions and even Windows or MacOS.
So your potential user base will be pretty big.