Difficult to put it in words: Better soundstage, naturality, three-dimensionality... After I switched the m-scaler off after listening to it for a long time, I thought everything was so digital, and the soundstage somehow collapsed into a less-dimensional experience; some naturality disappeared, and I could not stand it. It is a matter of time; initially, the perceived differences were quite subtle, but after a long time with the M-S, I perceived it much more strongly. In short, try it for as long as possible before forming any judgments.
I even bought a second M-Scaler for my second Chord DAC. It is almost impossible for me to listen to music without it after having it for a long time...