I bought this to power my Superlux HD-662 EVO and my Superlux HD-681 EVO headphones and I'm very pleased with this little box. (You can check out my reviews on both those headphones if you're interested.)
But this thing... It's pretty much exactly what I was looking for. It does what it's supposed to - you plug your headphones in and you adjust the volume of the headsets individually.
What I would have liked to see on this thing, however, would be some small rubber feet because it's pretty light weight and tends to slide all over my desktop.
I also feel like the knobs could have had deeper ridges but that's entirely subjective.
I really don't have much more to say. It does what it's supposed to without any oddities. The price point is right on spot too. If it had weighed twice as much, had sharper knobs and rubber feet it would have been a 5/5.
I like this little thing.