I recently set up OS X Server 10.4 (Tiger) on an old G4 for my home office use and so far it's been running beautifully. As I was learning how to get it up and running, I created a blog to document the process. If you're starting off on a similar endeavor, it might be helpful. If anything, it'll give you an idea of what setting up OS X Server entails.
The link to the OS X Server 10.4 tutorial:
http://www.s2studios.com/blog/osx-server-104-tutorial/
I also put together a tutorial on setting up the AMP package (Apache, MySQL, and PHP) on OS X client and server:
http://www.s2studios.com/blog/apache-mysql-php-on-os-x/
Take a look if you're interested.