Idea being to give a window maximum space without going full-screen.   

This is one feature my daughter would find very useful.  Webkins is designed for a 1024x768 screen so viewing on her netbook 1024x600 the title bar and black message bar make it so she can't play webkins.  (Webkins won't allow full screen for some dumb reason either and refuses to make any changes)  -- well I lie she can she I just have to keep reminding her about the ALT mouse move thing --

If we could hide the title bar for specific windows it would give that bit of extra space.  Have it like a shade near the top window, or pop up like a dialog box from a hot corner on the window or key stroke.

The other place I'd find it handy is virtual windows like rdesktop and vnc, I'm constently using ALT Mouse click to move it under the black status bar.