It's a good, versatile headphone amp that does very well for the money. This kind of highlights the crappy value that the Violectric V200 offers, though.
I own one, but I'm selling it because I want to maximize synergy in my signal chain with each component. My main headphones are LCD-X's, HD800's, HD650's and DT250's.
I've used it with:
HD800's
HD650's
LCD-X's
LCD-2's
DT880's
DT250's
Q701's
HE-400's
Pro 900's
I think it has the best synergy with Hifimans and Beyers. With the rest it has been good and very listenable, but left me wanting more.