I use Ubuntu for work and Unity is an unmitigated disaster. I receive reports in many different formats, PDF, DOC, JPEG, HTML, PNG etc and need to refer back and forth between them.
Pre-Unity this involved glancing at the bottom tool bar and clicking the report name.
With Unity - I have to stop and think, "where is the switcher" oh yes it's on the left. Move the mouse to the left and then wait for it to appear. Now I don't know what format the report is in so I have to start at the top with Firefox and work my way down the different programs. If I am lucky I only have a few reports in each format and if they are distinct I can spot the one I am looking for with ALT-TAB. However more often than not I have to switch into the report to see if it is the one I need. If I have more than say 15 reports open I can forget where I am and go around in circles looking for reports. This rigmarole takes forever and is mentally draining. I have swapped back to Gnome2 now and it's a great relief.
Mark Shuttleworth - the man who snatched defeat from the jaws of victory