Direct Metal Mastering ( DMM ) LPs. What is this?

How do they sound, different?
Some say they are harsh and shrill.  I've found them just fine.  I don't let it stop me from buying one and if it a recording I already have and like I may add a DMM to my collection for completeness.  Specifically, Dexter Gordon's One Flight Up and Jackie McLean's Let Freedom Ring are excellent and compare well to their non-DMM counterparts.
I think it's like a lot of things - no one factor is dispositive of the outcome. The Stockfish LPs are DMM and they are some of the best analog recordings I've ever heard.  So I wouldn't make a record purchase decision based on whether it was cut to lacquer or metal.  
The newer Rush remasters are also DMM. I am not a big fan, but did wear out some of their cassette tapes back in the 80's.  I was thinking of trying one of them, but the DMM is a slight deterrent. I suppose just asking Acoustic Sounds would have made sense. 
I have quite a few of the Stockfish LPs and find them fantastic.  I also bought a few of the Rush reissues and there are fine.

I know I have several other DMM LPs and can't remember them being anything but good.
Momentary Lapse of Reason is DMM mastered and sounds super great.
Many records would have DMM etched and not mentioned on the album cover. It was popular method of mastering in 80's. Even some disco albums found in good will for quarter maybe DMM. Not a biggie in terms of value, but sound pretty good in almost all cases.

Momentary Lapse is absolutely boring music....also he's clearly Anti-semitic.  
Stringreen, I completely concur to your statement and don't care much about the music. I only described one of the highlights in DMM mastering in this particular album. 
I also intend to examine weather any statement is antisemitic or not. A war causing damage of any casual population by any side to control the territory or resources I would never justify no matter what side is taken. Also note, I was born in Jewish family, but prefer to be religion free.
Statistically and factually no Pink Floyd songs and albums ever motivated any kind of depopulation of any kind or feud between different nations alas from Badenweiler March(for example) so considering any of them anti-semitic may not have any valid point.