Honestly, the only con I haven't liked was Furlandia---but, in their defense, when I went, it was their first year. It was just very small, so there was little to do, and very few people to talk to, and there was a lonely dude who got overly-attached to me who was hard to shake *because* the con was small and there were so few people.
I find I either have a great time at AC, or just a so-so time. It's a matter of managing my expectations and goals, I think, as well as my energy.
I enjoy DenFur quite a bit, aside from the current convention space being a pain to navigate.
I've also historically loved BLFC, and I miss GLFC, because its small size allowed me to attend panels I might've normally missed, and have really nice, leisurely extended conversations with folks.