Refresh is disabled much of the time, and when it isn't, it doesn't do anything.
Even removing a directory from the search locations and re-adding it wasn't sufficient to refresh the font list properly. And oh yeah: When you remove a directory, the giant list pane still shows the list of fonts that were in it. So there's a glaring list-refresh/management problem.
Eventually I restarted the app, and at that point it still showed an incorrectly rendered font family (from a TTC file that I had since deleted and replaced with individual TTFs extracted from that file). When I installed one of the typefaces, it finally refreshed the renderings of all in that family.
This functionality is so fundamental to the application that I don't see any excuse for it being broken in a production release.