These things always cost more at first, so I agree that it's "overpriced" for the value it brings. That said, I think the practicality is that it provides all of the value of a phone and a tablet in a single device that fits in your pocket. It's a fairly large leap in the ever-growing list of other devices that smartphones are replacing.

I also like to think that long-term maybe they will have the ability to fold out along more than one dimension and potentially be dramatically larger than this, but that's just dreaming at this point.