Hi DCSingle,
I've made the trip several times from North Carolina to Kissimmee. This was two years ago (before I could convince my son and/or my sister to fly). I doubt much has changed. I liked the fact it was an overnight trip. We slept most of the journey. I would rather do that than drive down. I was much better rested.
If you're a light sleeper you might have difficulty since there is some movement. I recommend not getting a seat near the front or back of the car. The automatic door opening & closing can be disturbing. There is also a light near the doors which stays on all night. I solved this problem by purchasing a sleep mask. If you opt for one, try it on to be sure it shuts out all the light. You might also consider ear plugs.
We took a soft sided cooler with drinks and snacks with us. The boys took gameboys, I took books on tape. I recommend one of those portable dvd players. I took my laptop to play movies but the battery only lasts long enough for one movie so we had one going down and one coming back. I took Disney movies and we had quite a crowd of kids sitting all around us trying to watch.
I also took flannel top sheets for cover and on the second trip we took our own pillows. They have some small ones but they go fast.
All being said, I would rather fly for 1.5 hours but I would opt for the 14 hour train trip over driving 10 hours.
As to having a stranger as a seat mate, I guess it would depend on the number of passengers. Only one leg of our journey was so crowded that I saw only a few empty seats. The rest of the time people were spread out.
Let me know if you would like further details.
Carolyn