My daughter recently moved to Vancouver. I was in Seattle for a work trip so decided to take Amtrak to visit her for the weekend. This was my first real train travel. Overall, it was pretty good and probably is what I will do in the future in the same situation.
The train moved at a frustratingly slow speed (< 10 mph) for probably 30% of the trip, but aside from that I liked the more relaxed atmosphere of the travel and it was overall more comfortable.
The train itself was a bit bumpier than I expected and the wifi was not very good. Those things and the slow speed would mean I could not imagine taking a much longer trip than this one. With the extra time and hassle of dealing with an airport, this one balanced out as probably only being slightly slower travel but it was less expensive and more relaxed. If it were Seattle to San Francisco, as an example, the slowness would be too much for me. The comfort and amenities like wifi and food would have to be a lot better than they are.