In CS3, that feature was working like a charm but in CS4 and CS5 it became a pain. I used to work with hidden sidebars and in CS3 i could use it very often. But in CS5, I have to use tab or shift+tab shortcut key to show and hide them.
Here is an example. I put the mouse leftmost of the screen as a reflex. But it can't get the black transparent band to show to toolbar.
Note: It's same in Adobe Illustrator, too.