Rated 4 out of 5 stars

Great and much needed app. A few things that would make it even more useful:

- content folding or some other means to filter results to a specific css file
- better logic for hovers etc. If is never user, you can be sure that :hover is never used either.
- distinguish rules that are used but not effective (overwritten by another rule with higher specificity) from rules that are actually used

This review is for a previous version of the add-on (0.2.1).