As I remember, using font metrics detection on *nix platforms makes some delaying on GUI program startup (on *nix) - especially if there are many installed fonts. I wonder if switching to "internal" font metrics mechanism will eliminate this startup delay...
Well, interestingly, font metrics in X11 is exactly the next thing to do
I hope to make some improvements there, but what I have seen so far, I am little bit afraid that available freetype interfaces are not very favorable here. But I need to check it more..