I don't see many reviews for this new J6 tyre so I'll add my comments.

I had experience with previous J5 on a friend's Myvi with size 175/65R14. Tyre is approx 2 years old.
Comfort and quietness is pretty good. Very similar to previous experience with Mich XM2 and Conti CC6
Dry and wet grip for daily use is very acceptable, didn't really get to push the car since it's a Myvi not a sports car.

This got me interested to try the new J6 on my own Myvi G3
Just got it fitted earlier this week, size 185/60R15

Stock Myvi G3 size is 185/55R15. Decided to up the tyre height due to firm suspension on the Myvi G3 which became unbearable.

First impressions (less than 100km):
Fairly quiet and very comfortable. Very similar to XM2/CC6
Dry grip is good.
Wet grip will test when I get to.

Will report back with further findings in a few months time.
Edit:
In case you're wondering,
XM2 is good for quiet and comfort and it's a very good well rounded tyre for daily use but it's too pricey especially for popular tyre sizes.
CC6 quiet and comfort is excellent but the dry grip is average and the wet grip is really quite bad.

For myvi G3 stock tyre is Goodyear Assurance Triplemax. Grip on this tyre is very good but compound is hard. Not comfortable and very noisy. The J6 and with +5 in profile height transformed the car. Much more livable daily now.