I received an email from Allan Odgaard pointing out that if you are using TextMate 1.x under OS X 10.9 (Mavericks) some bundle items will fail due to ruby 2.0 now being the default.
So I decided to give TextMate 2.0 another go - but the “disable anti-aliasing” option is no longer available in the preferences.
Horace provides the command line to use to disable anti-aliasing:
defaults write com.macromates.TextMate.preview disableAntiAlias -bool YES
Et voilà :)