I think personal devices could be extremely useful in class. I could imagine, for instance, that I designate a dictionary user per class who will look up words for us on their cell phone whenever we need some help. When the students are specifically working with vocabulary or a challenging text, everybody could be looking up words on their cell phones.
One of the points I disagree with is taking pictures of notes. One of the interviewed teachers says: “If kids are taking notes they inevitably miss some of the information, because they are focusing on writing things down instead of paying attention to what is being said.” I learn through writing, and taking notes has always been extremely important to me. It gives me a point of focus. If I am asked to just listen, I find I cannot focus as well. If I did not write something down and if I just took a picture of what the teacher wrote on the board, I would not understand it as well later. But this might be my personal learning preference, and I know that for some students writing is a huge hurdle. For these students, taking pictures with their cell phones might be a good idea.