I really like the way tags work in IQ. The tags pane's Nb count column is super helpful in giving me a quick overview of what I have in my tag system.
What might be even more helpful is if I can run a filter from the tags pane so Nb would reflect only a subset of what I have in my tag system based on status.

Some example use cases:

1. Using tags as categories for tasks: I would want Nb to only count "open" or incomplete tasks
2. Using tags as categories for bugs (software bugs): I would want Nb to only count "open" bugs
3. Using tags as categories for coupons: I would want Nb to only count un-expired (valid) coupons
4. Using tags as regions for leads: I would want Nb to only count live leads

I think a simple way to do this is to tie the tag pane to the grid that's right next to it. For each of the use cases above, I can make a grid that has the desired filters, and have the tag pane's Nb count to reflect what's in the grid (plus a count for items with no tags)

When used that way, the tag pane would be used primarily as an informational pane of the categories of "stuff" I have in a grid, and to quickly see how many items I have in which categories. In those cases, hiding the display of empty tags (tags with no items) might be helpful since I am more interested in seeing the tag hierarchy and less interested in assignment of (empty) tags to items.