I have noticed in some posts that with the new Mountain Lion I need to purchase OS X Mountain Lion AND OS X Server to upgrade my Mac Mini server (even though it came as one bundle when I originally purchased it). I have no problems with paying for both but I am wondering what the upgrade is going to do to my settings. As I see it, the old OS X Server is not compatible with Mountain Lion, therefore, if I upgrade my server first to OS X Mountain Lion and then to OS X Server will this remove all of my settings (took me ages to get it working the way I wanted)?
The Server application tries to import the settings, but don't count on it to work. Wait for at least one more maintenance release before you upgrade, and even then, upgrade a copy of your system as a test before you deploy.