I violently AGREE! The 520 was a great touring bike and TREK lost its roots when it discontinued it. I put 48,000 on mine and I wish I still had it. The fork on the Checkpoint is not rated to take panniers and the shorter chain stays shift the load too far to the rear, making it too light in the front and hard on the rear tire. Stock Checkpoints can't get below about 27 gear inches. I love the REI ADV1.1 - it too is a touring specific machine with touring specific components.
I just looked up the REI ADV1.1, it's currently 40% off at $1019, with good looking front and rear racks, bar end shifters for reliability far away from home, Deore triple and hydraulic discs. That's a deal. Says "Discontinued. Shop now for best selection." YEP.