It's not portable in the sense of an iPod or an iPhone where you carry it around with you in your pocket. It's portable in the sense that you keep it on your desk at home, grab it and take it to work, then sit it down on your desk at work.
The design is not for everyone, but I think when viewing it through this use case, it has a much more successful design than a flat form-factor like most portable music players
(i realize this is two days old, but i just saw your reply)
But... they could have just made it flat, and then it fits the use case you laid out AND the pocket one. Like, there is zero advantage to the bulky shape.
The design is not for everyone, but I think when viewing it through this use case, it has a much more successful design than a flat form-factor like most portable music players