I'm not sure how you're advertising this little experiment, but I can tell you that I don't know a single designer/InDesign user on the planet that would NOT want to thin out their font menu. Apple's insistance on not allowing us to manage ALL the fonts – or at least keeping the mandatory fonts to a bare minimum, is about as annoying as it gets and we all get a little hot under the collar about it. If you really want some professional feedback, perhaps send a press-release to CreativePro.com and other related sites?
That being said, in its current implementation I can't see using it in a working environment. It's a fantastic idea, and the little I've played with it last night, it works perfectly. But it does need some changes in the WAY it works (my opinion, of course).
The main thing is the lack of the ability to dock it with other ID Panels... as it is, it "feels" like a separate app (which I understand that it is). If it were an official ID plug-in, I suspect the adoption rate would be much more to your liking.
The second thing I see is that entering names of fonts to filter manually is actually quite difficult because the font list isn't scrollable while you're typing in the preferences dialog. A better implementation might be checkboxes in the Font Selector list itself (checking the box would be the same as typing the font name in the preferences).
One more item. The size of the app's main window resets to the full height of the screen every time it's launched. It would be much better to respect the size it was set to at the time of quitting the app (or InDesign). This of course would not be an issue if it were an ID panel, but if it must remain as a "3rd party" window, then this would at least be quite helpful.
