There is a bug in Snow Leopard that disables LCD (sub-pixel) font smoothing on many third party LCD displays, including models from Dell, Samsung, LG, HP, EIZO, and Lenovo. Here are the details:
Snow Leopard introduces simplified Font Smoothing options under the Appearance pane in System Preferences. Prior to Snow Leopard, the available options were:
defaults -currentHost write -globalDomain AppleFontSmoothing -int 2
The number 2 here corresponds to Medium - Best for Flat Panel. You may also use 1 for light smoothing, and 3 for strong smoothing, as per the original OS X font smoothing options.
Mac OS X Hints
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