I honestly think Gideon was headed in that direction from the first episode. He was always...off. I mean, look at "The Fox"--when he starts screaming in the middle of the house? Everyone in that scene looks startled, and it's kind of scary. I read somewhere that EAB originally wrote Gideon's exit as a suicide, which makes much more sense to me than his ~riding off into the sunset~ exit, because suicide is where his character was going from day one. You can see echoes of the suicide idea when Reid walks into the cabin in 3x02, and in Gideon's scenes in 3x01--when I watched through the series and hit that episode the first time, I honestly thought that Reid had walked into the cabin and found Gideon's body.

Ugh can I marry you for your opinion on Haley? She didn't marry a man who would never be home; she married a lawyer who would be home for dinner and there to help her raise her son. They both loved each other, and still loved each other in "100"--they just couldn't make it work. And honestly, if I were in Haley's position, I would have left as well. Hotch is a good man and a good father, but he wasn't honestly a good husband.

And honestly, I never took that phone call as Haley cheating, which is what baffles me about so much of fandom reaction. She moved in with her sister at the end of the episode--I always assumed it was her sister calling because they were talking about Haley and Jack moving in with her for a while.