i had a gen iii model, sent it in to wally/chris j at parts express for their level 1 upgrade, was in it for over a grand with the upgrade
did not like the sound, was more detailed and extended, but sibilant, sometimes too aggressive, changed from stock tubes to various old stock ones that were smoother but i could never get the upper mids up to sound sufficiently non-digital - had other dacs in the same rough price range at the time, a schiit gumby, ayre codex and mhdt tube dac, all to my ears were more musical and transparent...
sold it after trying various things, and messing with it for over a year... often wondered if it could be improved by bypassing the volume pot
oh well, glad others seem to enjoy it ...