I ordered this just to try it in my 2015 Gibson SG Standard (to replace the defective brass zero frets that are fitted to the 2015 models).
It is fantastic. It claims to increase harmonics. It does. Sustain has improved in length and quality. Rhythm is creamier without losing any of the SG bite or growl.
I fitted it along with new strings, so it's too early to report whether tuning stability has improved. It seems fine so far.
To put it simply, it is a massive improvement on the replacement nuts issued by Gibson (and I have the earlier version gun-metal colour version and the titanium version Gibson finally settled on).
I'm so impressed with this product that I've just ordered three more. One for my 2015 Les Paul Standard and two spares. I'm already wondering if this is enough - they won't be around forever!
** UPDATE **
Having played-in new strings, I can say that the tuning stability with this Graph Tech nut is much better than with the Gibson titanium nut. I generally tune one string at a time with theG-Force on my SG (I think the guitar is too resonant to tune polyphonically with G-force) - and now I often find that the SG is still in tune straight out of the case. There certainly no more "whirring" backwards and forwards. Big improvement!