Qt 4 was supposed to fix font rendering. I remember that it worked for a while but then it stopped.
Finally, I have found the reason. It ignores my subpixel setting in
.fonts.conf (sure, what else would it be). In addition you have to add
Xft.rgba: none to your
.Xdefaults or run:
echo "Xft.rgba: none" | xrdb -merge
Now it looks exactly like I like it (and the same way as it looks in Gtk+ and Qt 3).