Actually...just to slightly correct...

Almost all of the Harmattan applications are written in Qt, but using the MeeGo Touch Framework (MTF), formerly known as DUI. Many of the apps themselves were already in development when the N900 went to general release. Because the apps themselves were in advanced stages of development, it was decided that they would not re-implement using Qt Quick/QML, however, MTF is all but gone in MeeGo proper (it's still in gitorious, but the handset community stuff has been systematically replacing all of it.)

-Thom