I've encountered a lot of issues on Windows XP with QT/Angle but also quite a lot on Windows Vista/7 where the graphic drivers by default don't support properly OpenGL or pretend they do but don't answer properly to Qt's requests. This ended up with a big chunk of my users having a blank window or even no window displayed to them and no way to reliably detect this on our end.
This feature has been in the works for multiple months now and I'm really glad to finally see it ship officially with Qt 5.4, so congrats to the team!