Works well enough, but it's obviously a v0.1.1 Rated 4 out of 5 stars

MemChaser works well enough, but it's very obviously an alpha. The memory usage seems accurate. Although it doesn't match Task Manager (lol), it does match Process Explorer, and that's what matters.

It'd be handy if it implemented the functionality of this addon, saving me an addon:
https://addons.mozilla.org/en-US/firefox/addon/memory-restart/?src=search

They definitely need to fix the little red button. I don't want in in the bottom right. I either want to disable it or throw it in the menubar along with all the memory information. Resetting the position constantly is just downright annoying. I already have 20 other little icons down there from other addons that insist on throwing crap in the statusbar. (Or, sorry, it's an "Addonbar" now)

I'm very interested to see what MemChaser reports after long browsing sessions. After a while Firefox goes nearly unresponsive, consuming gigabytes and gigabytes of memory and locking up for multiple seconds at a time, every few seconds. My suspicions are Firefox is crumbling under the weight of all my addons - its javascript engine just isn't robust enough. But since Mozilla hasn't added anything that can help me track down which addon(s) are the biggest culprits, I'm left with the option of installing more addons to help diagnose it. Hurray. :P

Well, MemChaser looks like it'll help.

This review is for a previous version of the add-on (0.1.1). 

You could disable extensions step by step to figure out which of those are causing the high memory usage. Otherwise check about:memory?verbose which lists compartments for websites and extensions. Probably it should be easier to figure out the causing extension. In any case it is worth filing a bug on Bugzilla. If you do so please cc :whimboo.