The NEC is nice but it’s still pretty slow. I wouldn’t want to go much more than New York to Boston. I took Boston to DC once and it takes 8 hours .. it’s like a 1 hour flight.
Yep. The Boston to NYC train is almost always my choice compared to flying. (Driving would be faster but I hate driving into Manhattan though I could drive to New Haven and take commuter rail from there.)
But, while I've done it, Boston to DC doesn't really make a lot of sense unless I'm looking for an excuse to do some reading, etc. for a day.