Keep up with the comparisons.
The Yggy has left the building! On its way to the next home trial.
Concluding Impressions:
The good news is that the slight (and it was slight) brightness of the Yggy had gone by the time it reached 8 days warm-up - I was out for a couple of days, so can't be more specific than that. The not so good news is that I didn't experience any sudden jump to magic land after 158 hours, or thereabouts

. The Iggy merely got better and, based on other recent comments, may well continue to improve slightly with even more time.
So, bottom line comparison against my Nagra CDC:
The Yggy is more open, detailed, dynamic, focussed. In particular, it creates a larger, more 3-dimensional "headstage", where each image is more clearly defined. Despite the extra openness and detail, it is also slightly less fatiguing than the Nagra - by virtue of the Yggy being able to more clearly separate out complex sounds. I felt that these improvements were across the frequency spectrum - I didn't notice that the alleged Moffat Bass was any more Moffaty than the Moffat Mid or Moffat Treble. But then I don't specifically listen out for individual sounds when comparing - I just enjoy the music and decide which one better gives me the "you are there!" feeling.
However, the differences are not huge: Going back to the Nagra is not at all unpleasant. It just sounds a little bit softer, thicker, mushier, but still a very good sound overall. So, considering the huge price difference, a very good result for the Yggy, tempered by a slight disappointment of not hearing that 158-hour-magic-boost.
Diversions
The TOTL Tellurium Q balanced cables really complicated this comparison. They were my intended partner for the Yggy, so I had no option but to burn them in concurrently. The TQs had similar characteristics to the Yggy as above, and in combination brought a substantial lift in these areas compared to either my SE cables or a sensibly priced XLR cable (Sommer "pro" microphone cable, excellent vfm btw if you don't believe in fancy cables). Moving the TQs to the Nagra gave it an Yggy-style boost, but not to full-blown Yggy level. Switching around SE/Balanced/Posh/Sensibly-Priced cables soon gave me comparison fatigue, so I stopped doing it.
Computer source impressions
I briefly tried the Yggy USB with my Windows 8.1, JRiver and Yggy ASIO driver. I was getting comparison fatigue by then, so all I could register was that the SQ was in the same ballpark as the Nagra CD transport, and I'll think about the details another time.
To buy or not to buy?
I'm going ahead with my Yggy order, presumably to arrive sometime in July. Had it cost 4 times as much, I may have thought harder about it. But it doesn't, so I won't. When my actual Yggy arrives, I'll make use of my posh Power Conditioner, fuses, etc, so it should get better still

)
Final Question
How come, even after 8 days, my Yggy's case temperature never got higher than lukewarm? Even Schiit's website describes it as getting "hot".