dxw00d:
Did you have the IDE open while editing the preferences file? When you close the IDE, it updates the preferences file with whatever all the current (to the IDE) values are.
Yes, I had the IDE open. So I tried changing the font with the IDE closed and that solved the problem of the font not getting saved in preferences.txt, but the new font still wasn't being used. So I uninstalled the oft fonts, installed the ttf version and used this line in the preferences file:
editor.font=Source Code Pro,plain,12
And now it works!