For me Gnome (2 especially) always felt more natural and productive to use than Unity. Besides, you could easily customize your Gnome to look and behave exactly like Unity but you can't replicate the same with Unity.
Gnome 2 always annoyed me because on every fresh install I had to spend time moving the two separate task bars to be just one. Vertical real estate is at a premium on all monitors, why would I ever want two bars taking up precious space?
I love that feature. One bar for the various menus and the other for the list of open windows. I often have several versions of the same application open while working and it is easier for me to find the right window on the open window bar than the alt+tab interface. When I upgrade Ubuntu again, the first thing I will do is install Gnome 2.
Never made sense to me.