Exceedingly useful, particularly when used with other tab managers like Simple Tab Groups.

A regex engine would be nice in future updates too. I'd like to be able to close, say, www.youtube.com, but not www.youtube.com/Username

EDIT 11-15-25: Add-on seems to be distintegrating in later versions of Zen (Firefox). Sometimes it closes way more tabs beyond the criteria I give it, sometimes zero tabs show up in it at all. Still a great add-on when it works.