heh I indeed use it quite a bit myself
That said, there are plenty mastering engineers among my customers, maybe they just don't like to share their 'secrets' ?
It has a dual function for mastering: first of all problem solving, more specific fixing non-mono-compatible mixes: DrMS can 'save' sounds that otherwise get lost on mono-summation. Secondly, it can work as a spatial (width/depth) enhancer, to create more space and/or definition. That can for example give an ITB mix a more 'analogue' soundstage.
As always, use subtly during mastering. The extreme settings DrMS can do are more for a specific part during mixing stage.