I just installed Mate on top of Ubuntu by the following commands:
sudo add-apt-repository "deb http://packages.mate-desktop.org/repo/ubuntu oneiric main" sudo apt-get update sudo apt-get install mate-archive-keyring sudo apt-get update sudo apt-get install mate-core sudo apt-get install mate-desktop-environment
Which caused no problems, but many things (window theme, Mint menu, ...) are missing.
It looks like:
But it should look like:
How can I install the missing packages?