I'm able to update apt-get to fetch hudson. When I start the service it reports started successfully; but, when I got to the console I get an error complaining about Xstream not working with this release of the jvm.

The work around is to install openjdk, switch the jre to be used (sudo update-java-alternatives -s java-6-openjdk) and start again.

This probably requires an update to the documentation for the ubuntu install page.