Absolutely the leg room, leg room, leg room (and pre-assigned seats).
DH is 6'3" so leg room is a big deal for us.
Even if SW did fly out of one of our nearby airports, DH would want to fly JB because of the legroom. I booked our trip down to MCO before I booked the return flight. Could've gotten a slightly better fare on Continental coming back to EWR, DH said no, he wants to fly JB for the legroom. The leather seats are very comfortable.
Additionally, I think DH would be annoyed with not having a pre-assigned seat and no guarantee that we could sit together, like on SW.
We love the TV's in the seatback. And, I would never make a decision on which airline to fly based on this alone, but we love that they serve DD coffee. America runs on Dunkin'!
Agreed about JB not changing their schedules drastically and ruining your seat selection. They did change our flight down to MCO by 15 minutes. No big deal, and they did not change our seat selection. On the other hand, last year we flew Continental, and they messed around with our flights in both directions, not once, but twice, resulting in the new schedule getting down there four hours later and getting home 90 minutes later. We lived with the change on the return flight, but called them on the flight down, and had them put us on an earlier flight closer to the original schedule.
Agreed about JB not overselling seats. Some people may not care since they figure that if bumped they could get a voucher for future travel, but in some cases, this is no good. When we flew Delta five years ago to get to our
Disney Cruise, they started bumping people and I started panicking since the next flight was not until three hours later, which would have put us into a race to make it to the port in time for boarding the ship. Luckily, we got onto the original flight, but I learned my lesson. Fly down the day before if at all possible. If not, try to fly an airline that doesn't oversell.
JB seems to have learned from its mistakes in February. That said, Bavaria (travel guru that he is

) has pointed out that one reason they had such big problems is because they are not a legacy carrier. That means that they could not book their passengers on the other legacy carriers once those carriers were back up and running. That is one reason passengers were caught in the airports for days. Planes in all the wrong places, and couldn't put passengers on other airlines that had planes in the right places. That said, I'm willing to take that risk. YMMV