This is beginning to sound less painful ! Driving does have some merits- as someone mentioned- you are in control !

And I have noticed that the air fare one way DCA-BOS has gone up to $300 from $98 on Delta this past week. Will it go back down again ? Did I wait too long and miss a good sale ?

I wanted to follow up and say that when OW tickets went on sale yesterday on AA airlines for DCA-BOS at $54 we decided we would fly. I appreciate the help everybody gave me regarding this question.

I'll add my two penn'orth, even though I have not travelled that route. I have taken the Acela from New York City to DC, and loved it.
I like trains, though. Being on a train in the United States, travelling between two big cities, is rather romantic for a Brit, at least for this one.
Why not give it a go? If you hate it, you won't have to do it again, but at least you'll have given it a chance.
Make it an event by bringing a bottle of wine, or a flask of best tea/coffee, reading a book you've always wanted to read, or jotting down your plans for whatever dreams you have as you clickety-click along.
Let us know how you get along, even if you don't take the train.
Nigello

We do plan to take the Acela from Boston to NYC. Should we buy tickets ahead ?

okoshi-

I'd recommend making a reservation for the Acela. The trains can sell out depending on time of day and you can always cancel/reschedule if your plans change. In addition, reseving online will save you a ton of hassle and time at the train station as you can pick your tickets at a kiosk instead of having to stand in line at the ticket window. Also, I'm not sure if the special is still running but Amtrak was offering heavily reduced fares if you book your tickets in advance (I think it was 14 days but I can't remember.

Thanks- that's a good suggestion

Sometimes there are specials available. When we took the Amtrak from Baltimore to New York awhile ago, there were two for one specials available. I just googled Amtrak discounts/specials and found it.