some notes that might be useful:

1)folds to pressure - this is helpful if you see the player fold frequently to
1/2 pot bets on the flop. It tells you to be aggressive with the player to steal some pots and also tells you to get out of the way if he re-raises you, he's got something. "Passive" also works, but "folds to pressure" (FTP) tells me specifically what my stance should be on the flop as the player would be unlikely to call unless he has me beaten.

2)I think your PFR notes are also helpful, 3.5xBB with that player means premium cards, limps mean worse than that and crap a lot of the time. You have to watch carefully for that PFR'ed hand of his that shows down, though, to make sure he's consistent and doesn't do it with 7 2o on occasion. Even more useful is identifying a player who limps with AA, KK, etc. with multiple limpers, I tend to be more careful with this player if he shows aggression post-flop unless I have better than TPTK. This player is not necessarily good, just tricky.

Notes are more useful, imho, with passive/rocky players with regards to exactly how to play situations. With Loose Aggressive players, much less
predictability exists and notes are less useful although if I am looking at a
table with a lot of notes saying "LAG" on players, I pass unless I feel like playing tight that session.