I may see two ST-10 at my airfield, but only after a few beers at the airfield pub
....
Spare availability is definitely an issue, as only about 55 were built and about 30 are said to be still flying (one, interestingly enough, in Tahiti). However, in climb performance and (to a lesser degree) cruise speed the ST-10 its superior to the non-turbo Arrow. And so far everybody I meet is curious about the a/c, which I honestly quite enjoy ...
When it comes to maintenance, we count on the guys of Diamond, whose main facility is on the other side of the airfield. They could do some engineering for minor parts, and they are a Socata service center. That's mainly about the TB and TBM series, of course, and Daher-Socata no longer has the STC for the Diplomate. But some inside knowledge hopefully has survived.