Rated 4 out of 5 stars
This is a good first stab at a Yammer Firefox plugin. Though, while it borrows code from Twitterfox (which I love), it misses some key features:
1) The option to set your username and password in the plugin, versus the inconvenience of having to log in on the site first
2) The ability to manage multiple accounts.
But all in all, a much-welcomed alternative to keeping Yammer open in a tab all day.