Here was my response to a similar question in
this thread.
Obviously, the larger the player population the less useful specific notes are, so at the PP 10s you won't end up at tables with players you've made notes on too often.
Still, I think it is a useful habit to get into. Even if you never get to use a particular note to make a great laydown or bluff later on, by regularly taking notes you are forcing yourself to pay attention to your opponents and evaluate their play and not just play your own cards or make generic decisions based on the situation.