If you have a MultiMonitor setup, on my system 2 monitors with nvidias twinview, there would be one major screen with the panel from the gnome shell and one without.
Now if one opens a program, developed with the new gnome guidelines, one probably has to access the globalmenu on the major screen, even though the program itself can be placed on the minor screen. This leads to really long mouse movements (and thats not really user friendly)
The best and easiest fix for this problem would be, if the shell/activies-bar would be copied onto the second monitor. Also there would be the overview accessible without the really long movements.

Ubuntu solved this problem (obviously and I just stumbled into it) with the moving top bar of their unity desktop. (moving I think wont be the solution because it breaks the touch flow if you have 2 touchscreen)