GNOME 3 has wide variety of support of themes and extension in its very begining development stage. It always depends upon the individual choice whether to choose GNOME or Unity. If you are have just installed GNOME SHELL in Ubuntu 11.10 you might prefer to see various awesome themes and extension available for it. There is slighty different in installing GNOME Shell. Here are the complete instruction to install GNOME themes in Ubuntu 11.10
4. Log out and log in back
3. Select the favorite theme that you want to install. You can look at 10 Best gnome theme.
4. Go to Advance system >>Themes>>Shell Themes and select your favourite themes from there
Most of the themes package are not packaged correctly. In such suitation you need to follow the follow steps to install GNOME themes
1. Make a new folder called .test in Home directory. Make sure that dot(.) is in the beginning of the test folder. You can user command called mkdir .test to create new folder name called test in home directory
2. Press CTR+H(make sure it is not assign for other shortcut keys. It helps to show the hidden files and folders
3. Extract the theme in .theme directories
4. Select the the from your GNOME tweak tools that you have install before.