I completely missed the existence of stsf, thank you for the pointer.
I read up a bit on why it failed, and the main reason (judging from mailing list posts, at
least) seems to be that the various X hackers (e.g. Havoc Pennington and various GTK hackers)
felt that fontconfig was good enough. And in all fairness, that is probably completely true if
you don't care about network transparency. I've never heard any other serious criticism
against fontconfig except for the client side rendering issue.