Travelling in any kind of tunnel is no more claustrophobic than this is it?
Remember there are two passenger compartment mockups, this is the smaller one we are referring to: http://i.space.com/images/i/000/031/716/i02/hyperloop-passen...
Unscientifically I'd bet less than 25% of people would be willing to ride in that for more than 10 minutes, much less 30-40.
Yeah, that's a little bit more claustrophobic than your average underground train.