The problem there is that the train system is so slow and unreliable. Much of the DC Metro system seems to be built on single track and the trains are really slow. Most of my friends that make long distance commutes ride chartered busses. A better way to ride, but still a long commute.
DC Metro is slow and unreliable? Are you talking about the correct thing? The DC Metro is excellent and usually features 2 tracks.
If you are talking about MARC real trains, somewhat correct. Camden line is a freight line, part of the oldest line in the country, and can be a bit slow. Penn line is passenger, though, and is plenty speedy.
Neither of which matters when at least you can rest, work or goof off while waiting for that commute rather than having to stay alert and not make any mistakes during it.