One of the big things for me is that lots of people frequent ALA, and the smaller crowd allows more personal interactions between fans. I made tons of friends over the past 3 years I have gone, and it is always nice seeing them again, since that is the only time we really get to meet up and spend time together.
Also, because it is more lax than say AX or Comic Con, the fans have more say in things, like all of the cosplay gathering threads you see. I'm trying to petition a Struggle Tournament, myself. Most other cons would have fan-made events on a wait-list a mile and half long, but ALA is different just because it is so laid back. It is one of the only cons I go to and not feel stressed.
Captain Jack Harkness: 5%
Booker Dweitt: 5%