I searched the web and maybe the whole Apple Discussions for this problem*. It's amazing how some people just says "I like font smoothing", others "don't like font smoothimg", "it's a Windows problem", "it's an Apple problem" but the solution itself, none. To be honest, not even me. The point is that I want to completely disable the Safari feature (and Safari alone, the only software that presents me font smoothing).
I've tryed several things like mess up with preferences, use a nightly build of Webkit and some other mad science, all no effects.
The last solution is we all who wants to have the feature "no font smooting at all" report that to Apple. One request only doesn't make any difference, but if we all request that they may pay attention.