Disable Anti-Aliasing Fonts in Xcode 4.4 in Mountain Lion
From the Release Notes: https://developer.apple.com/library/content/releasenotes/DeveloperTools/RN-Xcode/Chapters/Introduction.html#//apple_ref/doc/uid/TP40001051-CH1-SW680
Text and font rendering on OS X v10.8 is optimized for Retina display. On a non–Retina display running OS X v.10.8, some font configurations can appear blurry in Xcode. 11486875 Switch back to non–Retina display optimized text and font appearance in Xcode by enterin this command in Terminal:
defaults write com.apple.dt.Xcode NSFontDefaultScreenFontSubstitutionEnabled -bool YESIt worked for me on Mac Pro running Xcode 4.4 on Mountain Lion.
I also had this problem when upgrading to ML. System Preferences > General > Untick 'Use LCD font smoothing when available' seemed to fix it for me.
lifjoy's answer didn't work for OS X 10.8.2 and XCode 4.5, so I have found another solution:
defaults -currentHost write -globalDomain AppleFontSmoothing -int 0