I've tried the QT integration example from the wiki on Windows 7, Qt 4.7 and SFML 2 but it didn't work as expected. The screen flickered between the parent widget's background and the SFML graphics.
To fix it I added this to the QSFMLCanvas class:
QPaintEngine *paintEngine() const
{
return 0;
}
I took the idea from an OGRE3D Qt widget.