I bought one of these and I'm quite pleasantly surprised. With Edition XS it sounds extremely detailed and actually beats my ifi Micro BL amp in bass control and upper midrange clarity. I had the original Heresy a while back and I thought it was fine but not amazing. Got Heretic as a temporary solution while I wait for another amp build, but this thing actually has me looking forward to using it.
Looks like the switch to OPA1656 chips really helped. I remember liking those in the Geshelli Archel 2.5, but that amp just didn't have the power to really make more demanding headphones come alive. With 6 of em in parallel it takes that transparency and brings the power too
Gotta say tho, if you aren't a fan of a dry sounding amp, this isn't gonna be for you