No problems with my Conti. Not even with the super aggressive E10 (10% ethanol) when driving in Europe. Actually E10 even fixed my car, the fuel gauge is working again.

But really, a good car that was designed for RON 95 shouldn't have any problems. Maybe Japanese cars aren't so good and require higher quality fuel? With the difference in fuel price who would want to use RON 97 if they can get along with 95? Except for petrol station owners perhaps who want you to buy the more expensive fuel.