It's smallish here on the Mac running FF. Mac users have the ability to increase font display size using the key combination CMD +, which makes it easy to configure individual sites.
My very limited understanding of ms type fonts is that they use a built-in scaling agent which communicates with the display engine of either the browser or the OS. When I open TFP with Safari I get a slightly larger, crisper display than in FireFox, requiring no font size adjustment.
I've learned to live with the new font, but today it started to bug me again. I downloaded a FF plug-in that displayed the font for the selected text. The font came up as Lucida Grande. After looking around this seems to be a Mac font that many PC users have problems with. I also saw a note that installing Safari will install the font on my PC. I took a stab at it and while it does display nice in Safai, in FF is still is blotchy and mushed together.