When windows are not maximized, the top panel is basically wasted space for me in Unity.
Is there a way to make it autohide? i.e. make it appear on mouse over.
You can't currently autohide the panel in Unity. It is also not a planned feature.
There are ways you could possibly make the panel autohide:
None of these are immediate or even likely.
You can make it transparent. With ComprizConfig Settings Manager installed and the Unity plugin enabled you can change the panel's opacity to zero under the Experimental tab. With a light background and light coloured text or a dark background and dark coloured the panel will almost disappear but the icons and menu links will still be there.
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