It sucks. Seriously. I bought one and regreted it the moment I hooked it up. It's like running your audio through a boss pedal. The distortion it adds should be apparent to anyone. Plus the headphone amp failed within a month. It was under warranty but......
It makes way more sense to save your money and buy a decent piece of gear.
I have C-control and Big Knob. Both of them are good, but Big Knob has a better interface. I haven't noticed any distortion with C-control. Seawolf Studios in Finland uses C-control in one of their smaller rooms.