I believe it'd be very well worth it. I'm sure there are downfalls to it, but off the top of my hand I can't think of any. As many mentioned there are some benefits to it over a plane. Tickets I would imagine would be cheaper as well than a plane, mainly due to they would be able to hold more than a place I would believe and the fuel used would be cheaper. Though I could be wrong on that.
This would also open up a lot of opportunities for people. Depending on the speed and travel time this could open up job opportunities for some people who don't want to move from their community, but are open to working in a different count/state. Could possibly encourage people to visit other cities and visit friends, families, etc. If people are able to visit an area cheaper than it would for them to drive it would help encourage them to visit other cities for shopping and such gaining more business for others.
It would also cut down on car emissions, some traffic, and road deterioration.
There's just a lot of positives in my mind for this not to be a good idea.