I've used it to some extent to stream to my airport. But with very uneven results.
at home it worked fine for ages.
at a friends place with his airport. Hardly ever works.
The installation is easy at least.
from the terminal type the command
sudo apt-get install pulseaudio-module-raop pulseaudio-module-zeroconf
you might need to reboot afterwards.
Ubuntu will automatically detect your airport device on the network.
You can switch to using it as a sound source from your sounds setting in the upper left corner of your screen.
Go the the tab named "output" if / when detected you will see your airport device.
select it , and try streaming something to it.
Here is a picture of the menu. My airport is broken, so I cant show you how it looks,but its just another sound device below the Internal one
There is a 5-6 second delay when streaming / switching songs while streaming to the airport.