I go back and forth between one-strap and two-strap bags, and they're both handy for different things. For longer point to point runs, like commutes and such, I'm happier with a backpack, but that's because I'm usually carrying a ton of tools and a laptop. For screwing around town, nothing beats a good one-strap bag.

I tried the chrome backbone and could never get it dialed in right for me. It was always poking and binding and so forth. Sold it, got a reload backpack, and I'm loving it. I can carry more than i really should, and it never really gets uncomfortable on me.