Excellent.

Removes the burden of a long-running browser: it's always as if started anew, regardless of how many tabs you have. Only the few recently-visited tabs are loaded and running, and all of the others got unloaded (just like a freshly started browser would have them). Really nice for machines without a ton of free RAM.

Useful, simple to use, high performance gain, and open-source. Highly recommended!

Environmental friendly addon

Love it, one of my must have add-ons.

Really useful extension, nothing to really complain about.
Simple, Light, Effective! I use it all the time

halved FF memory usage.

Saw a noticeable drop in the amount of memory my PC was using by about 20% after installing this add-on.