I have on some occasions made notes on other players, especially over aggressive players, I find them to be unpredictable, if I don't make any notes, and will play against them more cautiously when I come up against them, the next time we meet.
In large Tournaments I sometimes label final table players a different colour so that I know they have a chance of getting that far, but in some games they don't always pop up again. So in general I don't always give them the same kind of respect.
Poker is a fun past time for me and I will not use HUD software, I cannot use it in a Live game so why would I want to use it on-line, players can become too dependent on such type of software and are totally lost without it.
Only the other night I came up against a player who must have been Chip leader, I was in the top 50 with over twice as many BBs against many other players on my table, this player had 4X BBs over me so was doing really well. but within 20 minutes he busted out, It is always nice being in the top 5 players in any game but staying there is the hard part.
Notes or no Notes it doesn't always follow you are going to win, if you keep them religiously.
When the fun Stops, STOP!