I have a really hard time writing down notes while things are going on. I have very good memory but if I'm taking notes while something is happening, I often don't remember anything other than writing it down. If I don't take notes, my memory of events, topics and discussions is often far better. Writing things down post facto also does not help me much, other than I know where I wrote it.

However I find the act of discussing a topic helps cement things. For me, the engagement with a subject is what really helps me remember things, and I suspect writing notes removes that.