Rated 5 out of 5 stars
Ontopic: Works in FF3B4, nice add-on, think the FF default behavior is odd. If I wanna collapse the dropdown I can easily do it by clicking outside it, don't need no 'auto collapse help when only one tab is clicked to open' disfeature.
Offtopic: Just commenting to get this out of the experimental category. Pretty annoying that you have to log in to install. I don't know how to get a add-on out of experimental category, but maybe it is when a certain amount of comments has been made.
P.S. @Reem: for FF2 users there is http://remarqs.net/firefox/bumped.htm which has the same feature.