When you have the bookmark bar with some bookmark folders and you go on one the folders, it would be nice that after looking for a link in one folder if i go to the next bookmark folder to automatically open, not to have to click again on the bookmark folder, the same as in Chrome.
I very much second this request, it's still a problem in 1.4.589.29. It's quite irritating to have to click again to open each folder, instead of just being able to hover over them once one has been opened.
The automatic opening of additional bookmark folders is also the way it works in Firefox, Opera, and Chrome.
It's a known issue. It also affects the menus on the Browser menu bar.