A quick review of the new mouse (MX Master 3S) I just bought:
It's very nice! The materials feel very premium in my hand. I understand that doesn't mean much to most people when it comes to a mouse, but it makes me happy.
I like the controls a lot. I don't like moving my hands back and forth unnecessarily, so a back button, for me, is a nice feature.
It's pretty complex, and will take a while to fully integrate it's feature set into my workflow.