There's already a super-high-speed transit route between two major cities about 400 miles apart (e.g. Washington and Boston). It's called an airplane -- takes about 75 minutes, plus airport-related overhead on either end. This is the would-be 400-mile maglev's competition, not existing train service.

And yes, I'm sure the maglev would be more convenient and nicer and otherwise objectively Better in a variety of ways, but the capital expenditures needed to make these incremental gains happen is huge.

> If the train is only running once every half an hour or once an hour, people will end up waiting around for a train for longer than sitting in it.

No, people don't generally treat commuter trains the same way that they treat subway services and the like. They try to show up for a specific train at a specific time.