I've had the dAck for a few months now, liked the non-OS sound enough to get the DacKit for my work rig. Assembled the PCB kit about two weeks ago, still working on a couple small auxillary circuits: toslink input, battery level and error indicators; and an enclosure for this. Haven't done any serious A/B comparisions yet, but the two seem to be very similar in sound, highly dynamic and resolving with a dead quiet background. I am running the DacKit from a 12 V (10 cell) NiMH AA pack and have listened with Sony D555 Toslink, Gilmore V2, and Grado HP-1 mostly.
I'd like to hear the Shigaraki or Progression at some point, but these other models should be very competitive given the price and similar minimalist design.