Font Sleuth app $12 (mac) mini review on GoMedia.
I have been using this today and agree with GoMedia that it is very snappy, much more than other app I have used before. There two things I really wish were incorporated, more as preferences than anything else. One - I wish that if you pressed a keyboard key, say "U" it auto scrolled down to Ubahn, my first "U" font. Similar to how it works in Illustrator for example. And Two - I wish that when you double clicked on a font the "Display" Specimen detail open in the same pane, instead of a new tiny window. This should just be a preference and I know some people may prefer this, but I do not.