If you use Delta vacations without the last minute deals, you are eligible for medallion upgrades, skymiles, and MQMs. If you do use last minute deals, you are NOT eligible. As soon as you click on "last minute deals" you go to a site that is "powered by Site 59" (upper right-hand corner of the screen). It is not anywhere in the fine print anywhere but it places a note in your PNR that specifically states that you are not eligible for an upgrade. I learned that lesson the hard way. Calls to SMS and the GA wouldn't budge. It did book into U class and I received miles and MQMs but no upgrade (even though seats went out empty - Friday PM flight XNA-ATL on SkyWest CRJ900).