I ususally do take notes in lectures and I think that for me it makes it easier to concentrate and to remember later what was in the lecture. (Perhaps a main reason for taking notes in lectures is that this was the tradition around here.) There were rare cases that in order to try following some details I had to stop writing. It is also rare that I go back to these notes but it did happend happen several times. I am better at writing lecture notes for blackboard lectures. Presentations are usually too quick. Also with a blackboard lecture where the lecturer write everything on the blackboard it feels only fair to take a similar effort.
I saw some people using computer tablets so that everything they write is stored. I do not know how convenient it is.
