Forgive the slow response to some of the comments. Font Combiner's utility is intended to be as much in the facility to combine glyphs from more than one font

Forgive the slow response to some of the comments. Font Combiner's utility is intended to be as much in the facility to combine glyphs from more than one font and to adjust spacing characteristics and hinting to taste, along with scaling fonts to size for greater consistency. Hinting and vertical metrics are quite the rabbit hole across platforms. This is a good article http://www.smashingmagazine.com/2012/04/24/a-closer-look-at-font-rendering/ http://www.smashingmagazine.com/2012/04/24/a-closer-look-at-... Font kerning is very new to web browsers. So far as I'm aware neither of the fonts demonstrated at the top of the post contain kerning information. The heavy fonts lower down do. Font Combiner itself is still very new. Tracking or character spacing (as opposed to kerning) may benefit from some additional tweaks for OSX. This is outside of the scope of the current UI.