I am not a big fan of the new fonts. It makes me feel like I am using a Windows program rather than a Mac's :).
What was the original font?
OmniFocus' previous default font was Helvetica, which also happens to be Mac OS X's default font for "user-editable content." Ken gives a bit of background in this thread.
Have you tried adjusting the size of the new default OmniFocus font? Most OS X apps seem to use 11 pt. or 12 pt. Lucida Grande by default (e.g. Finder, Mail, iPhoto, iTunes, iCal, etc).
Last edited by Toadling; 2009-08-17 at 08:33 PM.. Reason: Suggested tinkering with font size to match other OS X apps