Aside from the whole "will they actually build it" debate, I'm worried that if they do, the capsule ceiling won't be high enough for someone fairly tall (let's say 6'5'' or taller) to sit in comfortably. I'd assume the height of the capsule will have some effect on the drag involved, as well as the necessary size of the tube, so it makes sense to make it as short as possible.

Musk himself stands just below 6', so he may not naturally think of us taller folk. I'd hate to have to slouch for the trip, even if it is only projected to be 35 minutes.

edit: dear tall people who have ridden in one of Tesla's cars: how's the headroom in a Model S?