Ubuntu Feisty will be out in April, and one of the pains of Ubuntu is the absence of some essential (propriety) packages.
The solution in Feisty:
There is a metapackage available in the multiverse repository of Feisty to make life easy: ubuntu-restricted-extras.
Make sure to have the multiverse and universe repositories set up.
sudo apt-get install ubuntu-restricted-extras
Installs for you:
This means: Firefox will have Java an Flash support, gstreamer will have mp3 support, and a set of Microsoft fonts will be installed.
Good news and life is getting easier with Ubuntu. 🙂