I've got almost 500 hours on my Mk2, and there is no question that my Mk1 is going back to PS Audio. The Mk2 is better in every way.
The new USB implementation obviates the need for the Matrix DDC for conversion to I2S that so many Mk1 users have in their systems.
I've got a Holo Audio Red streamer / Roon endpoint on order to insert between my Nucleus+ and the Mk2. It will have its work cut out for it to sound better than USB from the Nucleus+ ISO Regen setup I'm using now. At some point I'll probably pull the ISO Regen to see if it's even necessary, but I'm having so much fun with things the way they are.