I think it is remarkable that Diamond survived the issues they had with Theilert. It will be interesting whether they have learnt from Thielert's mistakes with the Austro engine.
In my mind there is no doubt that the Diesel concept has many advantages. Whether it is a characteristic of diesel engines or not I dont know but everyone who can should experience how quiet and smooth the diesels are in a DA42. Swap from a DA42 to any other twin or single and the difference is remarkable.
Diesel has of course other advantages. Like it or not the day will come I guess when lead is banned and if GA continues to diminsh in the way it has more and more airports will be reluctant to stock Avgas. Diesels are more fuel efficient and, at least in theory, should be more robust.
Time will tell and doubtless there will be a few more disasters along the way. Sad to say innovation is a dangerous game in aviation.