Excellent Add-On, Worth the Setup Troubles Rated 4 out of 5 stars
Major installation and set-up headaches but I persisted because I have used this in the past and it was awesome - a real time saver as you can monitor mail in all your gmail accounts at once, and then log in with a single click.
If you're having trouble logging in to your account once you've set everything up, click on this link from another reviewer Mint - it finally got mine working (thank you Mint!) (https://addons.mozilla.org/en-US/firefox/addon/gmail-manager/reviews/382642/)
This is a 5-star add on that only gets 4-stars from me, only because of all the time wasted to get it up and running. Thanks and keep up the great work!