Got mine running yesterday with xmos usb-i2s, sslv +/- 12 PSU and stock firmware (still waiting for my usb-serial to arrive).
My first impression is this DAC has really clear sound, decent treble and mid. Yet the soundstage isn't very deep and the bass is not adequate.
My comparison is based on the same amp and headphone and comparing r2r to my forssell mdac-2