This is one tool that is super handy for both students and teachers and definitely got a lot of buzz at our opening meeting with the Apple dude. And it is way easier than you think it would be. Here is a screencast to get you started.
I had a teacher ask me if there was a way to hide or remove students who are no longer in your class. The answer is maybe. It depends on if they are officially dropped from your class and appearing as red in your roster and gradebook. If not, then no, you cannot remove them until they have been unenrolled from the class. If the student is showing up as red in your gradebook though, you can hide them so you don't have to worry about them. Here is a screenshot to help you do it: