Rated 3 out of 5 stars
I used to like using this addon, before the developer revamped the whole UI of the program. Initially it was more lightweight and quicker than this version. I also realized that without gmail manager firefox loads up a lot quicker for me. I now use "Webmail notifier" which in my opinion is a far better choice, it doesn't take up a lot of resources, and plus not only does it support gmail it also supports other email programs such as hotmail, yahoo (though I don't check those). It offers basic functionality but that's all I need. Plus, one thing I like about it is that you can easily rearrange the order of the email accounts, on gmail manager I have to initially configure them in the right order which I didn't really like.
Initially all I wanted the addon to do is to have my gmail accounts on the top right, so I can select it one by one, but now it's far too complicated.