Ask almost anyone who flew a lot with the early !600 motors, and over the years has progressed to the current engines, and i'm sure it will reveal very significant improvements.
It all takes time to learn, sometimes from negative events.
Whatever you make, buying the Mk 1 version of almost anything,comes with the knowledge that things are likely to change from your original purchase.
Compared with well known overseas purchases, I think Jabiru have responded to to any negative aspects and problems encountered in a positive way, and with proper attention as per manufacturers recommendations, it seems to be apparent that many flight schools are getting very acceptable hours of reliable operation at a very acceptable price..
However, there are many aircraft that sit around in hangers doing next to nothing and if they're lucky,get to fly just few hours a year, but whose owners expect them to perform like they've just come off a production line, and sadly in the many cases, that ain't going to happen.