There is one more advantage to having notes in class that nobody has mentioned so far, perhaps because it applies more to graduate-level classes. I often find myself confused because some fact on the blackboard uses words that were defined a while ago, and that I forgot the precise meaning of. Also, sometimes it's hard to keep track of what bigger purpose does some technical lemma the lecturer is proving supposed to serve. When notes are available, I can often just look it up right there and then.
For this reason, I often find it helpful to come to seminars with my computer, and look up the paper that the speaker is talking about online.
