Qt applications have been using the Windows theme API to draw it's widgets since the Qt 3 series. This is why existing Qt applications already fit very well into the Windows Vista desktop.
Yet, there have been quite a few cosmetic changes to standard controls on Vista and many widgets are now fully animated, including state transitions, pulsating default buttons and progressbars. To address these changes, we will introduce QWindowsVistaStyle in Qt 4.3.
It will be made available in the public snapshots tonight so that our users can start to experiment with it.