saves a toolbar of space! Rated 4 out of 5 stars
I love this add-on. It does just what I want it to do. Hides the bookmark bar until I mouse over it. Saves a toolbar of space!
RE: The 2 users who can't make auto-hide work - I believe that after installing 'Roomy...' I went into about:config and changed a preference there that moved the tab bar down beneath the URL bar (the way it used to be by default). Then auto-hide stopped working. So I reverted the preference to default, removed 'Roomy...' and then did it all over again, but changed the preference first, then installed 'Roomy...'
(I'm sorry to say that I may have done all these steps in the exact opposite order that I just described. If you want to test it, try to remember if and in what order you moved your tab bar down. It was one way or the other, and I fixed it so everything worked :)