I love, love, love StandardML.

I respect the sheer power of what mlton does. The language itself is clean, easy to understand, reads better than anything else out there, and is also well-formalised. I read (enjoyed!) the tiger book before I knew anything about SML.

Sadly, this purism (not as in Haskell but as a vision) is what probably killed it. MLTon or not, the language needed to evolve, expand, rework the stdlib, etc.

But authors were just not interested in the boring part of language maintenance.