After some more testing
confirms what I've said really, with traction control on, if taking corners well and not pushing too far past the limit of grip inducing wheelspin the diff does a great job with no interference, just digs the tyres into the road and grips and grips, feels great, for what it does it's the best value mod I have done. Still, the ASR button (renamed ARS, for when you want to behave like one) has now found a use as it was only gathering dust before. Just need some rain to come along to see how things are in the wet.