Great idea! Several of us have been championing this idea here. We are evolving in that direction. I have questions about how the multiple tags would need to function. Do you need remaining effort and schedule dates rolled up? Do you need hierarchal tags?

What you see as the category tree now in the product was originally intended to be used for decomposition and breaking up functionality into non-temporal groupings.

Another feature in our backlog is custom columns and the ability to filter on those.

So many opportunities!

If you are just planing to use the categories as filters and to find items, one of the things some of us have started doing is making our own tags and using them in comments.

Thanks for the feedback, your voice matters most,

-bryan