Jon,
There were sliding doors on the compartments and a "curtain" for privacy. Food is a bit fancier with a compartment too. Get to Sanford early. There is a cut off on loading. First on does NOT mean first off though. A movie is also shown. We had "Get Smart". I believe dinner was at 5 & 7 but that may have changed. You will be called at your selected time (& you have a meal choice). Breakfast is whenever after it is announced in the morning. You may want to bring your own snacks. They are a bit pricy onboard.
As for arrival times, we were close to on time in Lorton on 1 of 2 trips. CSX sometimes causes delays. It is their track - & shaky at spots.
There is a CSX station just past the Amtrak entrance as well as a Conrad Yellington stone(?) loading facility. When I rode last October there was a CY GP30 parked & very photograpic! (Cross the Amtrak tracks & look for an overgrown service road on the right.)
The Sanford station is fairly easy to find - it's before the town. Lorton is right off an exit to I-95. Traffic north on 95 can be a pain & there was road construction for north bound traffic (and more than one crazy driver).
Overall it is a nice trip. In October it was cheaper for me to take the train than to drive - gas @ $4. Now cost would probably be more on the train BUT then there is no motel, gas or food cost. I used coach on that trip.
If you ever use coach, bring your own pillow. The loaners are about 1'X1' in size.
Would I do it again? Yes. They used to run a commercial to avoid I-95 traffic. It is nicer to arrive in D.C. fresh & fed.
Have a safe trip.
Jay