If it can be done in less than a full day, yes. Going between, say, Berlin and Stockholm or Munich and Venice, I’d take the sleeper train. Going from Stockholm to London or Madrid, though, I’d fly: as much as I’d prefer to take a train, a journey would take some 24 hours, with several connections (vulnerable to delays) and cost a lot more than a cheap flight.

Hopefully train connections will continue to improve, though.