In general I'd like to see much more community ivolvement and communication if you are planning on adding callbacks definitions. For example recently callback definitons were added to contacts, file-storage, and project-manager without any communication with the community. Only those who follow CVS commits had any idea what was going on.
At a minimum, when you add a new interface it would be helpful to post on the forums, and if possible discuss the interface with the community to see if it is generally useful,and if anyone has any feedback or ideas to contribute.
