In answer to the question, in my opinion, Jabiru make an excellent ultralight aircraft. A good performer and generally represent good value for what they offer. They are used extensively in Australia for training. The airframes have proven to be sturdy. Yes, I have had some limited experience with them. Never actually owned one although our club has quite a few. As far as the engine debate goes, well, I can only say that my observations bring me to the conclusion that most owners get good results as long as the operator pays close attention to the correct 'care and feeding' of it (particularly temps and cooling). After all, do you really expect to get the same ultimate product reliability as a Lycoming or Continental for a small fraction of their cost?
Jabiru can sell me a complete aircraft for the price of a Lycoming engine.