With gnome 2 I can put a seperate taskbar on each monitor and switch quickly between tasks with the keyboard or mouse. I also have another panel with buttons to launch my most common apps. Small amount of mouse movement and 1 click.
With unity I have to drag the mouse right to the far left or my furthest left monitor , possibly scroll through the icons , select the app I want, click it and then I have to select the window I want. Lots of mouse movement and 2-3 clicks.
Another problem I get is when launching a GUI app from a shell script , I load the app but then cannot dock it because it doesn't understand the relationship between the shell script and the app. This means I need seperate icons on my desktop to launch some apps.