MeeGo doesn't "just" support Qt. GTK+ will also work as mentioned above.
Qt was just chosen as the main "link" for apps to be compatible between different Nokia (symbian/maemo) and MeeGo platforms.

I'm no developer but just a normal user of N900. From a user point of view, I'm very happy that Maemo5 will be able to run at least some apps that are going to be made for future OS's.