We know this is good to have, but I find myself justifying it to my employer. Please pitch in on why a development team needs a build server.
Two main reasons that non technical people can relate to:
It improves the productivity of the dev team because problems are identified earlier.
It makes the state of the project very obvious. I've shown my management the build status dashboard an now they look at it all the time.
One more thing. Something like Hudson is very simple to set up - you might want to simply run it somewhere in a corner for a while and then show it later.