The very form-factor of the device subtly discourages you from using it extensively at your desk; it’s more comfortable on the couch or in the armchair. It wants you to be somewhere that your mind is clear.
In turn, he says, clearing your mind when you’re at work. I’ve seen this sort of argument for using multiple monitors (and workspaces, etc, etc) and for Instapaper (read those long articles on your commute); people really seem to enjoy using an iPad rather than a computer despite the criticism:
We’re not accustomed to this. You can pick up a TV remote, twirl it around, and run your finger over some buttons without triggering anything. It has very small hot zones that you’re unlikely to accidentally trigger.
Would be interesting if computers are marketed as workstations again, leaving this new breed for us to play with. iPhone competitors are often labeled smart-phones; there is no such convenient way to brand alternatives to the iPad. Will there be any?