Not that the stock shaft was bad, but I have found even better performance for me with the Miyazaki Kusala Blue in the R1. I've put together two very nice driving rounds the last two appearances with the combo, and the distances are out equal to the best spots I've put balls in the few years I have played this course. With this shaft in play, I could probably stand to do some more tinkering with settings to see if I could lose the slight fade, but that's easy enough to do.
I agree with your characterization of the stock shaft - not bad at all. I just like the responsiveness and feel of the Miya much better. I don't know that I was seeing any extra difference in distance.