Aside from feeling guilty about requesting a bunch of features before I'd even registered the program, I've been enjoying EagleFiler more and more as I play with it. So here it is: my first feature request as a registered user. :-)
I actually saw this feature in Notae 2.0, which I downloaded briefly to take a peek at. In Notae's tag window it had a column that showed how many items had a given tag. I don't know if EF's data structure would work well with this, but it would be a really nice piece of additional info for the tag window.
Amusingly, Notae didn't have the checkbox feature that EF has implemented so well. If I were going to use it, I would have requested that feature from them.