65,000 miles of almost exclusively S mode. I rode with the touring mode at first, because sport mode felt pretty snappy and abrupt. It took some training to throw off the muscle memory from using the throttles on my Road King and V-Strom, but once that was accomplished, touring mode became a dim memory. I've switched it on a couple times over the years to remind myself how it responded, but it just feels sluggish.
The engine braking doesn't bother me. Just like the throttle response, it felt weird at first in comparison to other bikes I've owned. But the same wrist control that goes into modulating S mode also goes into adjusting to the engine braking. In a lot of ways I actually like it; I think it makes it easier when riding on curvy roads, because you can modulate your speed just by throttle control without using the brakes so much.
I've never ridden a bike that's been flashed, so it might well be awesome. I've just gotten used to the way the S10 rides, and I've never found it to be the intolerable bucking bronco that others have.