Better to use ContentController, which is designed to work with a data object instance. Page_Controller is an subclass of ContentController. A ContentController instance also uses it's data object as a failover object. This is very useful, because you can refer to properties and methods of the data object instance directly in the template - if the ContentController doesn't understand the method or property, it passes it to the data object.
I have been trying to get this working, but don't seem to be having much luck.
I have a DataObject and a controller for that object, which I am rendering out in an associated Page template. All methods on the object render fine, but if I try and add a method to the controller, it isn't recognised.
Am I supposed to tie these together somehow manually?