Just got home a few hours ago from our first AutoTrain experience and we enjoyed it quite a bit and have plans to do it again!
There were four of us in a family bedroom - DH and I and out kids 10yo DD and 6yo DS. We were impressed at how efficient the check-in process is: pull your car up, take out belongings you want on the train, your car gets boarded onto the train car and we go in to check into the desk which was also so painless and hardly a line. We are used to flying from Philly where there is a long line for EVERYTHING and our travel day seems to be one large headache. The AutoTrain in contrast was so EASY and STRESSFREE!
We didn't realize how much we'd be fed on the train from the wine & cheese, to dinner to cookie snacks later plus breakfast, I didn't need any of the snacks I had brought for the kids. I knew about dinner and breakfast but not the wine & cheese snacks and cookie snacks later plus complimentary water.
Dinner was decent. The beef was probably the best dish, but the others stuffed manicotti, crab cakes, pasta and meatballs and choo choo chewies were all decent enough. Our family enjoyed the dining and lounge cars quite a bit. The social aspect of the train was also something our family enjoyed. It was fun meeting and chatting with other passengers and for the most part everyone was very friendly and social. The employees of the train were also friendly and helpful.
On our trip down we arrived in Sanford an hour ahead of schedule and we got a bonus in our van being one of the first off so we were literally checked into our resort and at the parks by 10:00 AM!!!!! That was an unexpected bonus day of parks for us!!
Oh the only thing that didn't work so well for us was the bed arrangements for the family bedroom. I didn't realize just how short the "child" beds were. While it was fine for our six year old, our ten year old did not properly fit on the bed. She is of average height too, so anyone with kids over 8, I'd say the beds might be iffy for them. She did manage to sleep curled up, but it wasn't the greatest night sleep. Although I know she did sleep b/c I had a very hard time sleeping on the way down, however on the way back I DID sleep and felt refreshed in the morning.
On the way back our train was right on schedule and arrived in Lorton right at 9:30, however this time we were one of the last cars pulled off.

We were out of the station by 10:45 with our car.
Another great thing we found about the AutoTrain is having our van packed up and no charge for extra luggage! We went over Christmas and were bringing all the presents with us as we left on the 20th. It was so awesome that we had boxes of presents plus all our luggage and packed it all up at home and never had to unpack until we got to our resort. And just having the van was a pleasure, we didn't have to rent or wait in any car rental line.
To sum it up for us: although the train took longer to get to FL, it was way more pleasurable and stressfree than the airport and plane. To me the air travel and the airport itself is very stressful and taxing and I'm usually exhausted by the time we get to WDW with the train I was relaxed, recharged and ready to go!!