Quick response - I challenged from MVPG 75K over to DL Gold in late 2011, and am now DL Platinum, and have never looked back. The fact is, though, I'm on DL metal about 95% of the time now. I still have AS Gold until the end of the year so we'll see what kind of pain I'm in in 2013
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My experience with upgrades as a DL Gold (which is what you'll challenge to) on DL is that you'll not find much success on long-hauls out of Seattle. But the same can be said of AS to the E Coast much of the time. If you travel through SLC to MEM, though, you should find yourself upgrading much/most of the time as Gold.
Dave