DC<->NYC/Boston is actually not bad (Acela or not). A lot more businessfolk so it's kept up more nicely. If you get there early enough you can get on the "Quiet" car. People are serious as shit about the "Quiet" car. Business class is pretty nice too (and surprisingly affordable).
Second it for the NEC (North East Corridor) from DC as far up as Boston. The train saved me on several occasions during this and past winters when snow storms snarled up the airways and airports. Although trains will also stop running at some point, it takes way more to do so.
In the case of travel between DC-NYC, it's even better since Union and Penn Stations are right in the hearts of the cities.
For example, flights were snarled for days and cancelled all day this last winter and I ended up getting a ride on empty, snow covered streets only plows were running on to the train that was still running with only slight delays.
Part-way through a trip from D.C. to Boston I ordered a sandwich and a can of ginger ale on the train. I did not specify a brand of ginger ale, but the clerk told me that they were out of Schweppes, and that he didn't want to bother charging me for Canada Dry, so he gave it to me for free.
