Just from what I remember from others' posts:
Excellent accuracy.
Stiffer recoil than some expected.
Marlin reliability: Excellent.
Kills game well.
Ammo can be a bit scarce in the middle of nowhere. That said, handloading will fix that. Ballistics are closer to .300 Savage than .308 Winchester. I assume you knew the rifle is in .308 MARLIN? It's a rimmed cartridge, basically the .307 Winchester with the shoulder set back a tenth of an inch to keep COAL down to spec. It seems to be catching on somewhat; I really hope it does. The LeverEvolution bullets are slated for release by Hornady this year as a component.
Thin rubber butt pads have been offered on factory rifles for 40 or 50 years. No news there, they work.
The 308MX is not exactly new, this is the second year for the rifle, third for the cartridge. Marlin's newer offering is the .338 Marlin, considerably more powerful.
I'd seriously love to own a .308 MX; I think it's quite practical, and if a bunch of fence-sitters like me will go out and buy them, they will catch on as they deserve to.