So far, the Linux ports for RHEL5/6 and Ubuntu 12 have been done and back-ported to Qt 4.8.5.
Ubuntu 10 is current work in progrsss as is Max OSX 10.9
Patches have been applied to the Linux 4.8 Qt distribution to avoid a polygon clipping problem that results in incorrect drawing of polygons using QPainter – this does not affect OpenGL drawing.
Edit: all the platforms except win32/64 are on Qt 4.8.5 with the clipping patch.