Rated 4 out of 5 stars

great idea. I like it
Dont know if this is the right place to report bugs.
but I will just go ahead and say it here.
With this addon, everything's slower.
Most noticeably it takes quite a few seconds to close a tab.
Using latest Nightly on Win 7 x64

The official discussion forum is here:

Its true that the addon in its present form is slow. We're working on speeding it up as we prepare it for a test pilot to collect data on whether this should be in Firefox.