this has to be the most legendary ride or trip of a lifetime
A lot to see out of the window, however most of the time is just waiting for something to happen. It would still be worth it though.
It's probably better if you can break the journey in a few places. Do you like long train journeys? Last year I travelled from northern Belgium to Warsaw in a (long) day changing at Eindhoven, Munster and Berlin. More peaceful than flying and stress free.