I would argue that if nothing else, it is important to take a mental note of who you are playing against. PokerStars offers a feature that allows you to click on a players avatar and write down whatever disparaging things that you have to say about them. Only you can see your notes, and they could be helpful if you run into that player again. PokerStars even takes this idea to the next level by allowing you to assign ?colors? to a person, and you can label those colors however you choose.
For instance, you could denote the color Red for sharks and Yellow for fish. This makes it easier to make a note on someone, and it makes it easier to remember your notes without having to read the text. There are eight vibrant colors to choose from, so you can have a grand old time while still being productive.
The most important thing to bare in mind in both cash games and sit and go's is who the sharks are. This may seem repetitive and obvious, but being able to identify a player as good or bad, is one of the most important aspects of being successful. That is where the notes can be helpful, because if you have identified someone as a shark, you can better manage your play against them. For instance, you may be more hesitant to call big bets from a shark then you would be from a fish.
If you are in it for the long haul, (you have no future aspirations and you want to play poker forever), it is a fun idea to date your notes. That way when you are fifty years old, and making a couple hundred dollars a week off poker, and making ends meet by ?relying on the kindness of strangers?, you can look back to when you at least had a full head of hair and get a real chuckle.