To install the Gnome Shell desktop interface in Ubuntu, and replace the horrible Unity interface which is only uniting Linux users in the common hatred of the Ubuntu distribution and driving users to the Linux Mint alternative in droves then simply install the packages thus:
sudo apt-get install gnome-shell
Then the desktop may be loaded with this command:
The users of Intel integrated graphics chipsets may need to execute this command to fix a graphics display problem.
The Gnome Shell desktop is not as bad as Unity and once a lot of themes and plugins are available for it, you will be able to craft a very usable desktop out of it. I can’t understand why Canonical did not stick with a pure Gnome 3 desktop for the Ubuntu 11.x releases, instead they crafted an execrable desktop interface that does not support customization and is only to try and bring in OSX users, but the software for the Apple Macintosh is pretty good and it is unlikely that all the Macintosh users will come over to Ubuntu due to the similar interface. But all the Ubuntu users are moving to Linux Mint, which actually cares about its users and they are making the Gnome Shell interface actually usable for their users. If they are not happy with something you are doing you should change instead of just continuing what you are doing. But Ubuntu is moving to a touch/tablet operating system and it will not be a desktop OS for much longer. So better to use Fedora or Linux Mint and leave Ubuntu to pursue their tablet aspirations alone.
It is not like there is only one Linux distribution after all.