"Did I end up with a "better" bike than if I had just gone to REI and gotten one off the floor? (Or LBS, assuming they would price comparably?)"
Absolutely, and not just for the fun and satisfaction of building it yourself. You've got quite a few components on there that are miles ahead of the stock pre-built, such as the Microshifts and the wheelset. I almost dropped an extra $400 on a double crankset and some 2x10 microshift bar ends.