
The left top corner is by default a hot corner for Gnome Shell. It displays thumbnails of all open windows when mouse is moved over there. Please remember it works only for open windows which are not minimized.
So, once I switched back to Unity, I wanted the same functionality as I kept moving my mouse to the top left corner to get all my windows! I had used this functionality before, in Ubuntu 10.10 and I knew where to find it! Easiest way to achieve this is by using a setting in Ubuntu Tweak. I am sure almost all of you will have Ubuntu Tweak installed. If not, then
Install Ubuntu Tweak or download the latest version from its website.
In Ubuntu Tweak , this option can be found inside Compiz Settings under Desktop. There, under sub-menu Workspace Edge Settings, from the dropdown menu of the top left menu, I selected Show Windows. That’s it! I was able to enjoy the same functionality as Gnome Shell to show all open windows.

"In Ubuntu Tweak , this option can be found inside Compiz Settings under Desktop. There, under sub-menu Workspace Edge Settings, from the dropdown menu of the top left menu, I selected Show Windows."Hello, I'm having trouble finding this option. I've looked in Ubuntu Tweak 0.6.0+20111015 and in Compiz Settings Manager, and I cannot find the 'Workspace Edge Settings' option. Can you help me figure out how to find that option, please?
These options have not yet been ported to Ubuntu Tweak 0.6 beta. If you are using the new ubuntu tweak ppa, install ubuntu-tweak-o package to get the old version . The old version has this option.