Of course, it doesn’t eliminate it entirely as that would almost certainly impact to some degree on the wet signal, but it certainly does remove a lot of the noise whilst playing! Best way of telling is playing really softly; on a normal noise gate, with the threshold set right, playing light will give you all the white noise as well as the light playing as the gate is open, whereas with the Zuul it’s cancelling much of the white noise out so you can actually here the soft playing. You’ll have to let their marketing department know 😉
There is a reason why they are raved about, but yeah it’s a lot of money. I got a good deal on mine, they’re otherwise around £250 to get one here, on a good day.