please note that there is an ongoing discussion of the Gradebook internal improvements that might have significant impacts on the Gradebook usage. We believe that the changes we are thinking about would bring useful features for advanced Moodle users while simple usage would remain simple.
There is a draft specification document at http://docs.moodle.org/en/Development:Gradebook_2.x_architecture that summarizes the planned changes. Now we would like to get a feedback from the community to see what you think of it. Thank you for constructive and thoughtful comments in advance.