Interesting
article in the Torygraph about sales of the OED on paper. It's kind of a special case because it is so expensive, but I think it shows a clear trend.
I certainly tend to use the electronic more than the paper form for dictionaries (both OED, but more often, the excellent Chambers application on the iPod). Paper dictionaries are still nice for browsing, but most people are more sane than to spend much time doing that, I guess
