I just saw one in action at my Trek LBS. It is way cool. You can hear a small electronic whirring sound when it trues up the front sprocket. It would be great for my arthritic hands because it just takes a very light push. I asked him about battery life & he said "forever" - hmmm...that's a long time. After reading this thread, I'll have to grill him a tad more about that.

One of the cool things is that because it's electronic, you don't have a cable to stretch out. It's just a wire & with the Madone, it is inside of the frame.