Its great to have a log or some sort of list to help you stay on task. What I love about these week challenges, is that it helps you visualize the finished project in your head and develops your workflow. And in your case they will also help you work with the overall scope of your game.
Optical Jam will be like a weekly exercise that will help you improve as a developer. I would highly recommend any game designer doing more jams like these.
And as far as the rating systems go, it has been removed this time but will possibly be brought back based on how many people are participating.