I don't consider wireless transfer to be critical, myself, but we would do well to remember that recorded music has always required some kind of technology to work, whereas books have not. I think ebooks and readers will have to work harder to be as convenient as their pre-electronic counterparts, whereas music players have gotten
more convenient over time.
I note that more and more digital cameras are now able to connect directly to printers. Completely different functionality, but same user perception of wanting to do without a computer.