As a professional you need predictability and consistency - two things apple have proven not to be when it comes to FCP and MP. Avid users on the other hand wondered what all the fuss was about.
Considering Avid didn't post a profit for nearly a 5 year stretch there, there's always the possibility your tool of choice could disappear...
Also, I disagree about the support jerkaround being the reason an editor would leave FCP. I think it's way more about how much of their work flow they need to retool and the money/retraining involved. I think an "all's forgiven" situation is not that hard to imagine if a person could see a reasonable path forward.