I couldn't find the topic but in the help section there is an article on, "How does the contract feedback system work?"
On oDesk, your feedback is your reputation, and your reputation is a very important part of landing jobs! All freelancers and clients may rate each other when a contract ends. Clients provide feedback on your work in six categories:
Not sure that helps much, but I have only had a couple jobs and two are long term contracts, so I have not had a ton of feedback.
On the original post I don't worry to much about feedback because I focus on doing the work as best I can. I have days I don't want to work just like others I am sure but I then think back to how I LOVE working from home!