A friend lent me the Bacch SP adio to use for about 6 weeks. It is a fascinating device. It is also hugely overpriced. The Bacch4Mac is a cheaper solution and probably nearly as good for a purely digital flow but it is still fairly expensive.
As for sound quality, the Bacch on many tracks makes a big difference in how the music is presented. The soundstage may widen and deepen, different elements of the music may be more forward or recessed, and even the tonality sometimes seems to shift. I would say I preferred the Bacch on about 90% of the music I listened to and I did have my system set up so Roon played the same track to the Bacch and to my DAC and I would switch between both from my preamp.
The issue I had, besides the cost, is not all music sounded better or even correct through the Bacch. For me I found it disturbing when certain tracks simply seemed wrong to me and I certainly didn't want to spend my listening life switching back and forth deciding which presentation I preferred. So even though the Bacch was better, often much better, on the vast majority of music, sometimes it was worse and I didn't like that. I think many people would find the tradeoff of 90% much better and 10% different in a way that seemed wrong, a very acceptable solution. Certainly, my initial reaction was that I couldn't believe every audiophile with a 6 figure system wasn't using the Bacch at least some of the time.
Truly, the unit should be priced like a mid-range DAC at $2-5K and I think they would sell thousands of units. The Bacch4Mac is an effort to do that but in a very kludgey and unsatisfying way. With its current pricing and product offering I doubt they will ever achieve much success.