I agree it's best when playing multiple tables or tourneys at a time. You can take notes on the players. How they may have played a hand. You can see if they're playing tight or loose.
Then after you can review your play and find your leaks.
It's very useful when you play on several tables , personaly I use it , I can't follow every action on all tables , so it notes a lot of useful information , so don't hesitate to use it