I have. Difficult to do a real comparison though because I changed rotor sizes too at the same time.
There does seem to be slightly better modulation though. It feels like I can control how much I want to brake, a little better, almost like the braking force is applied more gradually over a longer stroke. Unfortunately that could be down to setup, rotor size, different (newer) pads, etc.
Only thing I can say for sure is I believe the m8000 looks better.
If I can be arsed I’ll swap rotor sizes over the weekend and try and do some more scientific testing.
If you’re wondering whether it’s worth the upgrade – I don’t think so if you already have XT785
Chris.