Great analysis, thanks! Looks like the big value of going from UA to AS is the 100% mileage bonus and the waived change fees. Of course, if AS can't be counted on to preserve these benefits then there's no point in pursuing million mile status.

I'm surprised that AS does not publish the specifics of its million mile program as other airlines do. I think a lot more people would be inclined to pursue million mile status if AS would simply step up and publish the benefits along with some kind of assurance that the stated benefits would continue in the future. For example:

"After 1,000,000 flight miles you will receive the following benefits for life: a 100% mileage bonus on Alaska Airlines, service fee waivers on Alaska Airlines revenue and award tickets, and MVP Gold Status . . ."