After I received my frame, I pulled all pivots to grease and inspect them and noticed that on the back triangle only one spacer/washer was present on either side. The bearing is centered and without a spacer or washer on the opposite side, the frame will rub and you will have movement on those back pivots. I picked up some washers from the local hardware store...problem solved.
I would bet that the movement and creaking people are experiencing is caused by only one washer on the back pivots.
Edit: forgot to mention I went with steel washers, not nylon washers. I didn't want them to compress or distort around the bearing races.