I haven't been to Europe yet, but after living in Japan for a year and then returning to the US, there's nothing I miss more than trains that go fast and go everywhere. I could wake up, walk down the street, hop on the train, and be 350 miles away before getting bored of staring at the back of the seat. They've managed to get by without much cannibalization of other services (you can still get to anywhere on normal-speed trains) and it seems that revenue ends up being at least more than operating costs. They obviously make a great deal of sense in Japan, and perhaps less so in Europe and the US, at least for cross-country service. Regional services would be fantastic for key areas, and I don't see why we couldn't make it work. Unless we just skip right to Hyperloop?