Sorry to get back so late on this thread. I did finally receive the unit and I really appreciate what it does. The bass and lower midrange is thicker and stronger and overall coherence is better. I've had some friends have a listed as well and they were impressed. I've tried with the Sennheiser Amperior, Momentums, and Harman Kardon CL with good results.
I've found the Nomad LNG-W Lightning cable makes a great match for the amp, as it's nice and short and doesn't waste pocket space.
I did notice that the unit picks up on cell phone activity, however other similar devices do the same. The noise floor is average like Hapster said. In addition, the 3.5mm inlets can be finicky with odd shaped connectors (such as Harman Kardon CL). Overall I'm quite happy with the unit despite the caveats. The fit and finish is nice and the bump in SQ is really worth it, and it's still a steal (at $199) compared to comparable units.