Are you using the gradebook in Moodle 1.9? If so, please take a look at the list of usability improvements we're hoping to implement in 1.9.5: Gradebook improvements in Moodle 1.9.5.
As our proposed improvements involve changing the interface quite a lot, something we'd normally wait until 2.0 to do, we'd like to make sure everyone is happy with them before adding the code to the 1.9 branch. Teacher opinions would be particularly valuable.
Please see the discussion Wanted: User testing of Moodle 1.9.5 gradebook improvements in the gradebook forum for details of how you can help with testing and feedback.