Rated 3 out of 5 stars

Well, it does change refer header setting (currently using FX 4.0.1).
The status bar icon could definitely use some improvement. Due to small icons used in status bar now, it's barely readable. The color of icon changes from red to yel to grn for values of 0,1,2.

The icon is so small, unless you write yourself a note, you'll never remember / see that you changed the setting - assuming you want to reset it, soon after needing to make a change to get a site to work, etc.

There needs to be some option, some way - for those that desire referer header setting to normally = 0, to "remind" that the setting was changed. I find that when have to temporarily change referer header from 0 to 1 or 2, I forget to change it back because the icon is so obscure. (size of icon isn't developer's fault).

Or, have a default setting option that resets to default value chosen, once you've changed it to access a site, then close that page / tab.

Or, an option to have the referer header setting switch back to the selected default value after so many minutes / sec. AFAIK, once you've successfully loaded a page that needs a referer header setting OTHER than 0, changing referer header setting back to 0 won't affect that page.

This review is for a previous version of the add-on (0.40.1-signed).