I have this hooked up from my Metric Halo LIO-8, going out to my PSI A25s, Avantone MixCubes and two pairs of headphones. Soundwise, it's very transparent on the monitors, but does unfortunately add a bit of noise on the headphone outputs, causing me to deduct one point each for Handling and Quality. As I use the (phenomenal) headphone output on the LIO-8 for my main phones, this doesn't bother me too much, and the additional pairs are only used for quick reference purposes, so it's not a deal breaker for me.
My Avantone MixCubes have a slight humming issue (quite common, unfortunately) which the ground lift feature doesn't eliminate, but again, it's not a deal breaker and can't really be blamed on the 2Control.
The 2Control features and overall build quality are excellent. I can't understand why all controllers don't have Mono and Dim buttons, especially the former, as it's such a necessary feature for working quickly when you want to listen back to your mixes with the computer screen turned off, checking for mono playback compatibility. The main volume knob has a wonderful feel to it, it's big and travels smoothly, keeping the stereo image intact across the whole range, something that e.g. the SM Audio MPatch 2 doesn't handle as well.
The two headphone outputs are controlled by individual volume knobs (woohoo!), and shares a Crossfeed feature, enabling the user to simulate the interchannel bleed when listening to speakers in a room, as opposed to the 100% left/100% right stereo representation of standard headphones.
Noise issues on the headphone outputs aside, I found this to be a great monitor controller with all the features I need in my mixing and mastering studio.