I got into Criminal Minds sometime in the 1st season I believe, but I've seen every episode. Haley was always a great mother and did what she could to handle everything in their marriage. Hotch is pretty damaged after everything he's seen, done, and been through in the series. Even if he doesn't mean to, that stuff sticks with a person and he brought it home with him. Over time, it strained their marriage. Haley had to look out for herself and Jack while Hotch was always gone, and that didn't help either. Eventually, both Haley and Hotch made the decision to divorce. They never stopped loving each other, even when they were divorced. Haley didn't want to take Jack away from Hotch - she had to because of the Reaper.
I liked Haley. I wish they didn't have to kill her off, but I can see the point of needing to move Hotch's story forward by taking away the love of his life. I wish they'd show Jack a little more though, as it seems like he's fallen through the cracks. They have Haley's sister taking care of him, but it seems odd that she'll always take care of Jack in Hotch's new home while he's always gone, then he comes home and she disappears. I'm starting to think her and Hotch will fall in love so Jack's aunt will become his new stepmom. The show has been around for quite a few years now, so they're going to have to be stretching the backstories to some crazy places if they're going to keep the show going.