Originally Posted by rucksack

You could debate the merits of the program, but that's exactly what the Million Miler program is intended to do: provide recognition for long-term loyalty. The MM designation is visible to front-line staff so that they can provide personalized service to these members (that's not to say that they always do). As a 4+ Million Miler, you have complimentary annual Platinum status, which is incredibly valuable since you can redeposit award tickets for free.

As far as upgrades are concerned, no, I don't think you should get upgrade priority simply because you've flown a lot on Delta (or PMNW perhaps) in the past. Consider that even 360 members don't get higher upgrade priority (not that they would need it since most of them probably purchase F outright).