I have no insightful comments about the issue of laptop use in class. But I do have an observation/anecdote:
I am in a "seminar" class with 14 students. On Monday we were having student presentations; one student standing in front of the class talking, the other 13 sitting in a semi-circle listening. There was no need to take notes, we were just listening and discussing.
One guy in the class had his laptop on, and was playing solitaire throughout the presentations. I'm not criticizing him; I was busy doodling, and probably not paying much more attention than him. I'm just wondering about... I'm not sure how to put it... his lack of subtlety, I guess. Since there was absolutely no reason to be taking notes, there was no reason for anyone to be using laptops. I think that if I were the professor, I would have been looking at him and wondering "what the hell is he doing with the laptop?" And I think most professors are smart enough to know, without looking at the screen, that he was playing games or surfing the web. So, basically, he was openly playing solitaire in a class of 14 people.
I guess I just always thought that law school etiquette required students to make a reasonable effort to pretend that we're paying attention in class. For example, when IM-ing, we should try to look like we're actually taking notes. I think that any sort of laptop use at a time when there's no reason to be using one is a violation of that rule.