In previous emacs versions evaluating the following line would disable
antialiased fonts:

(setq ns-antialias-text nil)

That was broken in 24.4.  I'm attaching a patch that both fixes the
behavior and disables "synthetic bold", which looks pretty terrible with
antialiasing disabled.

I reported this on the emacs-devel list, but didn't receive any replies:

http://lists.gnu.org/archive/html/emacs-devel/2014-10/msg00833.html