The problem with OS X font rendering imho is that it produces heavier result than anything else.

I made comparison picture, and noticed that Adobe Reader renders text bit taller than others, but on the other hand it has imho best antialiasing. http://img154.imageshack.us/img154/5549/fontrendering.png

(Samples are from Windows/Wordpad, Adobe Acrobat(using pdf printed from Wordpad), Microsoft Word, Adobe Photoshop (sharp), in that order.)