Very useful add-on to make tab groups really practical for everyday use.
Currently I still see some glitches, especially when adding/editing regexes, where the add-on claims the rule was added when in fact it wasn't (probably due to a parse error in the expression).
Feature ideas: Add a full screen page for configuration with better overview when you have a lot of rules.
Offer config sync across multiple firefox instances using Mozilla sync.

Great experience! That was what I was looking for! Same functionality as the ones from Chromium based extensions. Thanks del-boy!