That’s probably because Snow Leopard now relies on your monitor to tell your machine that it’s an LCD. Unfortunately, many LCDs including both of my Dell displays don’t do this. So you get no sub-pixel anti-aliasing. Bad times.

But don’t fret. There is a solution. Open up a terminal window and type:

defaults -currentHost write -globalDomain AppleFontSmoothing -int 2

and all will be well again.