I just installed the Gungnir. After reading the various forums I narrower my search to the Eastern Electric Minimax Plus, the Teac UD-501, the PS Audio NuWave and of course the Gungnir. They all seem to have strengths and weaknesses, and are well reviewed and spoken about in the forums. What finally sold me on the Schiit DAC was its future modular upgradability as they come up with new and improved boards to swap for a reasonable cost. Thus, if their model succeeds and they stay in business for a long time, it has the potential to surpass in performance any and all the DACs I mentioned.
I can only comment on the sound out of the box. I've been in the hobby for 38 yrs. and never had a separate DAC, primarily because vinyl has been my mainstay. The focus, detail, dynamics and bass are substantial sonic improvement over the built-in DAC on my venerable Rega Planet 2000 CD player. I also hooked up an LG 570 Blue-Ray/CD player and an older Sony DVP CX850D 200 DVDs/CDs Carrousel with similar sonic results because of the DAC upsampling of the incoming signal. I connected the Rega to the DAC using the optical and the last two sharing the coaxial RCA with a Y connector. Since Gungnir provides two sets of analog unbalanced outputs, I have one connected to a Korneff 45 SEi (1.5 wpc)integrated tube amp, and the other to a B&K AVR 202 solid state receiver, so I can play all three sources through both amps. This will allow me to do rock and heavy organ music and video on the solid state, and jazz and classical on the tubes.
As I understand it there is a break-in period of about 100+ hours, so I expect the sound to get even better (or my ears to get more used to it :)
I can honestly say that the sound of digital is getting very comparable to my vinyl rig (Rega P5 w/Benz Micro Glider, EAR 834P phono-pre).
The build of the Gungnir feels rock solid (no plastic on the outside, all aluminum), and a no brainer to operate (just one selector push button). Also during my research I communicated with them a number of times asking questions, and I got a reply from one of the owners (Jason) within a few hours every time. Their customer service, even if you may not like the answer, is impeccable.
I apologize for the wordiness but I hope this is helpful to another audionut out there still on the fence on what to get for an external DAC.