I'm running a Novatec SS cassette disc hub on my Surly 1x1. Its rocking the 16tooth skinny cog that came with it. Surly and Endless Bike Co. make thicker based cassette cogs, so the cassette body doesn't get mangled as bad. Its on my list of things to get once there are funds.
Running a Surly flip-flop hub on my Fixie commuter. Running a surly fix cog on one side and an ACS freewheel on the other. No complaints so far on it either.