Huh. Weird that people are having so much trouble. I downloaded and started fine. I played with High textures and everything else medium, capped at 60FPS for the past ~5 hours and didn't notice any stuttering or glitching, certainly didn't have any crashes. I mean, yeah, it's a bit heavier on my system than I expected (given that I can run Skyrim with 4k textures and 200+ mods at 60FPS no problemo), but that's just optimization work that needs to be done.
--
Regarding actual content: The people who said "it's all the same" are full of shit. The only thing that was repetitive visually were the caves, since they apparently only bothered to make one generic stalagmite/tite and the hex-column iron block plus three colors of glowing plant. Looks mondo cool the first time, less so after that. Fauna and aboveground flora were massively varied, as were the geographical features.
The people who said that it only has 10h of gameplay or whatever are also full of shit. I'm 5h in and only on my third planet in my second system, still only have one suit upgrade and a slightly better multitool, am still on the starter ship, and I still feel like I've been rushing through stuff. Same with the people complaining about inventory space, amusingly enough--I've got seven of those suit upgrades already too, and I'm not trying to farm them.
That said, the flying sucks dicks. Seriously. It's fucking miserable. The ship handles like a bar of soap bouncing around a prison shower during a fight, the altitude limiter makes it next to impossible to see what's below you. And I understand why that limiter exists now, I'd be crashing left and right without it. The ship controls are a really loose and slippery mouse-point, W/S throttle, and A/D roll. That's it. Press E to auto-land, spacebar to in-system FTL. Flight needs some serious tightening before it is even remotely worth calling complete. Don't buy NMS if you wanted it for the flying, at least not yet.
On the whole, though, it delivers. It's the experience I wanted, albeit rough around the edges and with shitty flight.
e: Aaand there's already threads on reddit with setting tweaks to fix the FPS problem that people appear to be having. Might not have noticed it myself because I did a lot of it when I started the game.