Berlin-Munich high-speed train services carry 2M passengers in first six months
They had a "High Speed" line before, but it was on old tracks, and they had to use tilting trains.  I took it a few times when I lived in Berlin.  It was somewhat slower than driving.  Still, the ICE is an excellent train.  It's very punctual (Germans will complain when it's five minutes late), it's smooth, it's clean, the seats are comfortable, you can get a seat with a table if you want, there are power outlets, and if you get hungry, you can go get a snack, a beer, or a full dinner.  It's just just a civilized, pleasant way to travel.  The Internet, either through the DB system, or my normal 3G/4G tethering was a bit spotty, but I was nearly as productive on the train as I would have been at the office.  At six hours Berlin-Munich, it was much nicer, less stressful, and more productive en-route than an airplane, but somewhat slower.  At four hours, the train is a no-brainer.Air travel is the king of hidden time fees.  They say that it's an hour from Berlin to Munich, but you have to show up at the airport an hour before the flight, it takes 15 minutes to get off the plane and get out to the curb, even if you didn't check a bag, it takes 40 minutes to get to the airport, and another 40 minutes to get from the airport to the city center.  By the time you add it all up, 4 hours is how long it takes on the plane, and most of that is annoying stressful walking from one place to another, waiting in  one line after another, cooped up in a tiny seat, and for maybe 30 minutes of the whole 4 hours, you can use your laptop and do something useful.