Another nice option would be to be able to dock the toolbar to the side of the screen. If you have so long lines that the used horizontal space is a problem, it's probably time to rethink stuff anyway...
With the recent fashion of 16:9 screens, I have started positioning toolbars vertically, both for my Windows desktop (taskbar on the side, not the bottom) and for my own prototyping app (where the landscape orientation moves the toolbar to the right edge), just so I could save precious vertical space.
Personally, I'd prefer to hide the toolbar completely, but allowing it to be hidden or moved would help everyone get what they prefer.