First let me say that this product is built like a tank. It feels like it could put up with years of abuse on the road. However, in my particular case unfortunately it didn't solve the noise issues.
For those interested here's my setup and what I did:
Amp A is with a CFH wah, Big Muff, Greer Lightspeed, Wampler Tumnus and Catalinbread DLS in front of it on clean channel. Amp B is without any effects in front, running on dirty channel.
I plugged my guitar into A/B/T input on Lehle Dual SGoS and output A went into wah, fuzz, etc. and into amp A and output B was plugged directly into amp B. When only amp A was plugged in, everything was quiet. When only amp B was connected, everything was quiet. When both amps were connected to Dual SGoS you could hear a noticeable increase in noise. It sounded like cross between buzzing and humming. I pressed the ground and phase buttons in different configurations. The ground button when pushed out made the noise and hum so loud it was unusable, when it was pushed in, it was much better but still far from quiet. Essentially it was the same as when I plug into a stereo delay and split the signal that way. I also tried it with a big pedal board in front of amp B which only amplified the humming and buzzing issues. Once again if only one amp is connected things are relatively quiet but when a second amp is plugged in, the noise floor increases noticeably.
So in summary, even though it is a very convenient amp switching solution, unfortunately it is not a panacea for humming, hissing or buzzing issues that I was hoping for (at least not in my case). Maybe the problem was a power supply (although I tried three different ones), maybe the problem is with the electrical installation in my apartment (although it was replaced a few years ago). I'm not sure. Whatever the issue may be, my rig was not quiet as other people have stated in their reviews so even though I liked the convenience of easy switching, at this price point I had to send it back.
By the way, big thank you to Thomann.de for making this process so painless! Shopping for musical gear online is not easy but Thomann helps out musicians so that they don't get stuck with gear that may not be right for their needs. America has Sweetwater, in Europe we have Thomann! Thank you, you guys are the best! :)