Default Mac OS X settings make some fonts look ug-lee. Read JWZ's post for some details. Some fonts end up looking thicker and more jagged than they should be.
Here's how my Terminal and NetNewsWire looked when I had to re-install my Mac:
And after the fix, here's how they look now:
What fixed this? Go to System Preferences > Appearance and set Font Smoothing Style to "Standard".
