I always enjoy a good PSD bashing but don't like some of the inaccuracies...
The coolant filter was needed on PSD 6.0 because of casting sand left in the block, nothing to do with minerals in the water. For some reason, that block was not cleaned as well and over time, the remaining casting sand would find its way into places it should not be and plug things up, such as EGR cooler. When this happened, more bad things happened. Please note, not all the blocks had the problem, hence the reason that many of the PSD 6.0 are running fine with normal maintenance.
The head bolts were a weak area also which caused blown head gaskets which if not caught right away caused more bad things...
... and it goes without saying, if you combined either of these issues with lack of or improper maintenance, you were asking for trouble. Same with tuners, if you had either of the above problems, the tuners would bring big issues.
If you had no casting sand, head bolts with no issues and did your maintenance, you had a long lasting reliable motor (and just normal problems like everyone else has)...
Not a bad motor all in all, there are still many thousands out there running fine..
of course this is just my opinion and not an PSD 6.0 owner.