travla, thanks for your kind words! We always try to write our apps in a cross plattform manner to ensure maximum portability in either in Qt (like MouthPot) or in C++ and OpenGL ES like Sphyro 3D:
http://store.ovi.com/search?q=sphyro+3d

so if we publish a new app we can port it to Maemo quite easily since we already have the framework in place.

One interesting thing of Maemo is that there are only a little number of apps on Ovi Store so at least you get exposure for your app), but on ther other hand there are not so much N900s around so even if the app is free the number of daily downloads goes down after a couple of days/weeks.
And Maemo users tend to not buy apps and it is very easy to pirate them (no copy protection, the install file is simply a .deb).
So hoping to write a large app and make money from it on Maemo is hopeless. This is probably the explanation why there are so commercial few apps for Maemo.

Some stats about MouthPot downloads yesterday: Top #4 in free application on Ovi Store Maemo, num downloads: 1090, of which 77% N900, 23% Symbian.
On Symbian it's harder to get exposure since there are 10 thousands of apps, but if you get in the featured apps section or top 20-30 downloads you can make very high numbers.
Our Tron Legacy Door Code Unlocker Screensaver (only for Symbian touch)

http://store.ovi.com/content/99490

made around 14k of free downloads in a single day (it was in the featured apps on the Ovi Store front page). That is very impressive.

But even on symbian if you switch from free to paid then the number of purchases rarely goes over a few per day, so it seems like the free / paid download rate is about a few hundred : 1.
Even on Apple App Store and even worse on Android.
I have the feeling that the firms that run the app store do not tell us the truth that users are after all not buying so many apps after all like they make us believe (that writing apps is lucrative etc ).
Of course a few lucky developers can make nice sums but it's more or less like playing casino.
Often the stupied stuff earns the most cash while complex apps which took time to develop are ignored by users.

Another way to make money is putting an annoying banner in the app and require the user to have an internet connection. But not everyone has a cellular connection all the time and often it is costly.
So several developer make 2 versions: the free version with banner and the paid version without.
The problem with advertising supported apps is that you need to make quite a few numbers of daily pageviews per day. advertising firms pay you $3 per 1000 pageviews.
Since many apps get utilized only a few times to make 1000 pageviews per day you need 500-1000 downloads per day of your app. This is unsustainable on Maemo since the number of N900s around is limited. Even on Symbian it is hard to achieve those numbers over a longer period, therefore sometimes it is better to make 3 sales at $1 per day rather than having a free advertising supported app. Of course the opposite could be true too, but you need to be very lucky