Review for Gmail Manager by RaLX
Rated 5 out of 5 stars
First of all I agree with sateev, this is a free (or donationware if you prefer) extension so you should be civilized!
For me the extension is working fine, I don't have any log in problems, if you're having problems report to the developer in a kindly manner.
Personally my only complaint is that I don't like having one icon for every account in my status bar, I would really like to have them merged again (or just add an option for this).
To create your own collections, you must have a Mozilla Add-ons account.