If you have a Radeon with analog LCD panel and after upgrading something (possibly the radeon driver) SPAA suddenly no longer works for you in Qt4, try the following:
$ echo Xft.rgba: rgb >> ~/.Xresources
$ xrdb -merge ~/.Xresources
I'm too pissed off by this and debugging it for two days to offer any explanation (just to note,
Option "SubPixelOrder" doesn't work; if you feel like digging, see qfontengine_ft.cpp, libXrender's and libXrandr's source). Also, YMMV. If it works you're on your own to make sure it gets loaded properly.