How about added to the waterfall preview, we had a preview, where you can see what the font looks like in a paragraph and a title. It would make font pairing easier.
Not necessarily something as complex as the Google Fonts Type Tester, but maybe along the lines of the Layout section of Fontshare.com.
Here is an example: Fontshare: Quality Fonts. Free. (scroll down to Layout).
I also find it super useful that I can switch fonts in the title as well as the paragraph text.