Well I'm flying to DFW next week, and I am strongly considering JFK-DCA-DFW. I did this trip last week and it was fine, but I had to return to LGA due to scheduling.

If you are looking to take Ramtrak to another airport, may I suggest BWI. I believe the train serves the airport, and BWI's ops are a lot more reliable than DCA (longer runways, less congestion) and it is less crowded than PHL. But it will still add 2 1/2 hours to your trip.

Good luck with your decision.