I don't mean i want to run both GUI'S at the same time . I mean if I can install Gnome 3 and have unity-2D which I can change back and forth at any time by logging out and logging back in deciding what session GUI I want.
I am running ubuntu 11.04 with unity 2d on an acer aspire one netbook.
Ubuntu 11.10 uses Gnome 3 by default and yes, you can easily have both Unity, Unity 2D and Gnome Shell in it. 11.04, however, is based on Gnome 2 and cannot use Gnome Shell without fairly large changes to the system. I would wait until you're comfortable and upgrade to 11.10. Then you can just apt-get install gnome-shell. Unity2D really rocks in 11.10, btw. I know people who actually prefer it to Unity and it's actually understandable, though I prefer Unity myself. Gnome Shell is also very nice in 11.10. :)
I would not recommend using a PPA to get Gnome Shell on 11.04.
