Rated 4 out of 5 stars
Brilliant, although I agree with an earlier comment: "Could you change the color of the mask in the status bar when private mode is active?" ...Please.
Please upgrade to version 1.8 of this extension. It was just approved and should show up on amo within an hour or you can manually tell Firefox to check for an update.
Tools->Add-ons->Extensions tab, click the 'Find Updates' button.