I have two computers on my desk and I needed a product so I could easily switch between these.
A very well built product, solid metallic feel on the know, has all the buttons you need for switching between two monitors and two inputs as well. In addition, it has a jack-input (cable included) for mobile phone audio that - when connected - overrides other input so you can easily listen to stuff from a mini-jack device like phone or laptop.
The only downside in this product is that it has no headphone output. However, it does have two monitor outputs so you CAN connect your headphones to the other stereo output with correct adapter. Since One Knob doesn't amplify the signal, I can barely get a loud enough signal by maxing the One Knob when listening through headphones. The level goes way down when listening via One Knob compared to the original source so this setup won't work if your headphone has high impendance and you'll need an amp inbetween. I have closed AKG 2xx (don't know the model since the tag has worn away) something and it works with those with reasonable level. I was considering Sennheider HD600 and those have 300OHM - I very much doubt that this setup would work with them and the signal would turn out to be way too quiet without an amp.
Really solid product, can't hear any additional noise added and the quality seems the same, for what I can tell. Warmly recommended.