It is ok to make notes during a game, but it can cause friction with other players. Just as its fine to make notes on a particular hand to review later.
I have heard of some people using a dictaphone, I guess if you tend to speak in a sort of retorical way (sort of like Phil Hellimunth) then you could discretely make notes via a dictaphone and people wouldnt really realise that is what you were doing.
As the game moves very slowly (30 hands is per hour) you probably wont have all that many notes to make in the space of an hour, so its possible you could discretely make notes on players during the breaks or maybe excuse yourself for a 5 min break every hour or so.
What you need to remember is that a lot of people who play in smaller tournaments or smaller cash games are not all that serious about poker. The thought of making notes never even crosses their minds and when they see someone doig something strange that they dont understand they fear it. Now he isnt going to be so overcome with fear that he cowers under the table, but it will get some reaction, what exactly that reaction is is impossible to say, its probably going to be that he just thinks you are wierd. It might be that he tells
you this, It might be that he asks if you are allowed to do this with a view to you being told you cannot. It may be that he makes insane hero calls because he dosent like you and its his mission to bust you. It may be he makes big lay downs as he thinks you are a por and becomes very wary, who knows. It may be that he chuckles and does nothing.
The reason I mention this, is that I have heard a lot of live pros (not TV stakes but real life stakes) say that the key to table image is to blend in not do things that will make you stick out.. i.e make notes, dress like a stereotype poker player, not to berrate people etc, insted the key is to look and act "normal" be pleasant, keep people relaxed and happy and try and make your skill look a bit like luck.