These improvements to the quiz interface for students taking quizzes originally work out at the The Open University. You can see them in action here: http://labspace.open.ac.uk/course/view.php?id=3484.
There are two main parts to the changes:
- The improved navigation
- The changes to adaptive mode
The navigation improvements are now Complete in the Moodle 2.0 development version MDL-15452.
The changes to adaptive mode will happen later. See Changing_the_Moodle_Question_Engine.