You can create an app for N900 so quickly it will make your head spin. I followed the directions for installing MADDE, modified a hello world C++ QT app, did a make, and the app was runnable on my laptop. I did a make clean and did the make through madde and copied the file to my N900 and I had a running app on the phone. It automatically had the N900 look-and-feel, and just wanted some packaging to make it useful for others to install.

The only thing that took any time was looking up the C++ syntax I couldn't remember. And I want to spend some time making it look better and figuring out packaging before I think about sharing it with the world. But the point is that it is insanely easy--and even easier if you use Python over C++. Your first app might take a day or to to muddle through, but your second or third can be churned out very fast. And
the QT app can run almost unchanged on your PC or on symbian or on winmo.

I suggest you install Madde and QT and build the hello world app. Run it on your phone. At that point you'll see how simple it is. Then modify it to do something else like add two numbers or show the current time in big red letters. In a few hours you will have an app of your own. You can have an app posted to extras-dev for the rest of us to enjoy in less time than it takes to fill out the paperwork required to let other people see your app in the iTunes app store.