The statement about DL does seem a little misleading. It's not how much mileage you have, it's your current year frequent flyer status, and from what I understand the next determinant is time of check-in. In other words, for two equal level passengers whoever checked in first gets priority.

I still wonder though on the ATL-PBI flight that I was standing-by for on a Priceline ticket earlier this year whether it was the computer or the agent who made the decision not only to give me a boarding pass, but to give me a seat in First.