The GX500 "gaming laptop" makes no sense at all. A 860M to power a 4K display? What the ****? I doubt you'll be able to get good framerates even on low settings on any graphics intensive game at 4k. You need way more horsepower than any mobile card can provide, much less a 860M, to properly power a 4K display.
They've probably added pixel doubling scaling to the monitor, so you could play at 960x540 or 1920x1080 on the screen with perfect pixel scaling.
The 4K resolution and color gamut for digital content creation and manipulation is just wonderful. I'd buy this laptop because of its screen. For those not interested in the 4K screen there're alternatives like the Razer Blade which pack a GTX 870M and weights less. Or the Gigabyte P34G v2, cheaper.
I like the idea of Steamboxes. But it should have a replaceable vga card. Whereas high-end CPUs are just fine in the long run, games evolve graphically so fast that even the most expensive GPUs may not guarantee "high settings" in future games.
I'm looking forward to an upgrade from the G750, which is way too heavy with no possibility of CPU upgrades. MSI has got it right. Hopefully Asus takes a hint with their next full sized gaming laptop and get back to their roots of the likes of the Asus G50VT.