Banshee 2.2 final was released few days ago and landed in Ubuntu 11.10, but .deb packages weren't provided for Natty Narwhal.
Banshee official stable PPA has just been updated and provides now the latest 2.2 version final, so, in order to install/update the latest Banshee 2.2 add the following official PPA (Natty)
sudo add-apt-repository ppa:banshee-team/ppa
sudo apt-get update
sudo apt-get install banshee