When I tested the FR on the track, and on the skid pan - it's 100x better than the LCR ESP
ESP on with the FR, the back end still kicked out, but the ESP just brought it back in, so no fishtailling - even at 100+, hell you didn't even need to apply the throttle (really hard for me to work against my instinct!)
On the skid pan, induce a slide, and the ESP brought it back in tidily.
ESP off, the instructor really had to work hard to induce a big enough slide to actually spin me (lots of handbrake!!) but I was really working hard on the wheel & gas to keep it straight.
it's certainly not going to be a hindrance on your spirited driving, and since you're not going to know that there's mud all round the next corner, you'd be well advised to leave it alone (in the ON position)