Tilmann,
Building your own moving faders!!!
GO GET 'EM!!!
I am assuming you are asking about the noise of the physical fader when its moving?
They are relatively quiet, I really only hear them when I do a move on a sub group operating 8 or 10 fader, and its usually when they 'snap' back to a written level after i do a ride of 2db or more and then let go of the fader to get it back to its written level.
When monitoring audio, even at low levels, I almost never can hear the faders moving.
Any 'zipper' noise would indicate a fader that is dirty or in need of service.
Audio wise, they pretty much behave exactly as VCA faders, except of course they move, but no issue with slow fades, fast fades, and I notice no issue with accuracy.
Again, any issue with accuracy or overshoot would indicate a fader in need of service.
TLA