I would think.. sheer speculation.. that the most common apps is C++ right now. Like I said before, currently the pyqt4 libraries are non-optified. It makes it temporarily an unattractive solution because of all the rootfs full problems people already have.

I expect that in the future it will be the easier and more mobile way. Take my sig for example, I maintain pianobar and pyPianobar. Pianobar is a C++ CLI (command line) app, and my pyPianobar is, obviously, PyQt4. The pianobar requires I maintain two entire directories of the source code to re-compile i386 and ARMEL versions of the binary to run between the SDK and the N900. It also means you have to upload 2 packages to the extras-devel. (it may be possible to get the auto-builder to do this for you with a rules/make file of some kind: but pianobar has a weird cmake source, not a normal source.)

pyPianobar OTOH, allows me to just copy over my .py files wherever I need them, and just run it. From the N900, to the SDK to even a desktop computer it's just.. easier. Only need one package uploaded for both as well.

Don't get me wrong.. C++ is certainly a valid method. It's native, thus faster, has a lighter footprint, can run more intensive apps with less memory - and also gives you a greater control over the finer details of memory management and things of that sort. I just like scripting languages as a rule... Ruby, Perl, Python... they are more "fun" to me than C++ because they don't require as much work .