My two cents worth is that there are the following two camps:
Camp 1 - use it. Needed for debugging. Why would you not want to use it? Why take it out if you have it working?
Camp 2 - it's great to use it, but not really necessary as per requirements. Everyone seems to agree that it is VERY useful throughout debugging. Make sure if you include it in your submission that you do it right because if problems you will lose points. Also, you probably won't gain points by including it. (Although some have said they may have got their results faster by including fancy logging.)
I would say that if you choose to use logging, just make sure that it won't fail under any condition in your graders environment. (can't depend on the jre/lib logging properties file being there)
I would say that if you choose to not use logging, just make sure you do enough crude logging in your debug
testing to ensure that your stuff is working. Also document in your choices that you considered using it and decided not to for the following reasons...... From what my spec said, it sounds like as long as you document your design decisions, they don't break any required functionality, and you are consistent in your coding with your decision, you won't lose points. (Sometimes this sounds better to me than the potential of losing points if I screw some little thing up.)
Good luck making your decision!
TJ