Yea, having to awkwardly move around to answer a call when I have my phone charging is one of those little things that I suspect we'll all be surprised by how often this new feature improves our life.
It does seem to have promise. I didn't catch all of the details, was there a demo? Was it able to say, switch a call over to your mac with the ability to do something like FaceTime?
They did a demo call with Dr. Dre. They didn't showing switching a call between devices. I did notice a video button on the call on the Mac suggesting you might be able to switch from audio to video (presumably FaceTime).