Ulrik Petersen pointed me to How to use EMACS with Unicode Greek (polytonic Greek (multiaccented) included) and LaTeX.
"I can go back to using Emacs!" I thought to myself (actually, I probably typed it out loud to Ulrik over IM)
All that remained was to find a more up-to-date OS X build of Emacs. OS X comes with 21.2 but the greek.el above requires 21.3.
My initial Google searching found that a lot of Emacs for OS X work ended in 2003.
Then I stumbled across this: Carbon Emacs.
Emacs 22 for Tiger (with Universal Build).
The anti-aliasing is beautiful and greek.el works a charm.
Now to dig up my old .emacs file...