The system does not supply timely user feedback. For example, when I choose "toggle all" in my class list, it takes time for that request to be sent to the server and for the check mark to show up in that box and then to fill in all the boxes in the particular column. Good usability tells us that anytime a system has been requested to do something the user should get feedback as to the status of that request. The little clock or the apple hour glass - something that indicates the request has been made and action will be taken. I kept clicking the "toggle all" box because I didn't see any indication that my command had been received. By the time the system responded I had actually clicked and unclicked a couple of times and I ended up unclicked and had to start over.