Mark Antony's hangover -
Can you watch the classes live in real time? Or are they all recorded?
Both. If you like an instructor but miss their class you can retake it from the archieve at any time. Everybody that ever took the class will appear on the leaderboard and you can also filter to just see those taking the archieved class at the same time.
One other cool feature on the leaderboard is that it will also show your own PR as an entity you can compete against.