A+ - if you like tabs, then this is for you :) Rated 5 out of 5 stars
Love this addon. I realize that Firefox now offers "Close tabs to the right" as an OOTB feature, but this has MUCH more robust options (including my other favorites, "Close duplicate tabs" + "Close tabs to the left").
I saw the earlier comment about being incompatible with FF v22.0. I suspect that this was probably from an upgrade (I had problems with a lot of my addons for that version, but a fresh install / manual re-add fixed most of them). I have been successfully using Closy for (at least) v22 thru v28, and it seems to be working fine on v29.0 as well (fresh install). I am a very heavy user of tabs, and I use this all the time. Highly recommended.