So I spent 13 hours playing on the PS4 version with a buddy. Here's why I'm cancelling my PC preorder.
The entire animal and planet systems are generated from a limited pool of resources (textures, models, etc). You'll go to different planets that look slightly different from others, as in color palette swaps. I've seen plenty of animals that I've seen on other planets, just renamed and recolored. Sure you have 18 billion or whatever planets, but that doesn't matter. Most of them just repeat each other with a few different things.
Creatures, as I said, show up on other planets looking exactly the same, except with a new name or color. They also have no depth. You can feed one to have it spot resources for you (useless) or make them poop out items. That's it. Unless they're hostile, then they just run at you and hit you with no interesting fight mechanics.
Alien NPC's are incredibly static. They aren't interesting visually or in content. Really not much to say because they're that bad.
The UI is love it or hate it. Inventory management sucks post-patch still. Needing resources to power your suit, and multiple resources for different types of flight kills exploration. I get it's supposed to be "survival" based, but it's like they don't want you exploring (and finding out planets barely differ).
Combat is bad. It's clunky and simplistic. Not enjoyable at all.
Visually, on PS4, it looks bad. Pop-in like crazy, horrible FOV, textures that look like they came from an early last-gen game, or worse. Sometimes it can look okay, such as in orbit, but that's it. I'd imagine PC to look better but don't get your hopes up. Space also doesn't look like space. Doesn't look like the empty void it is. Instead, it looks like a fishtank or a tub full of bath bombs, with solid colors instead of blackness.
The crafting system is simplistic and uninteresting. All that can really be said.
The music is nice though, really atmospheric.
If this game were $30 it'd be fine, but at $60 and with how shallow the content is, it's not worth it. I'm sure in a week or two people will agree after naming planets harambe enough. Has potential to be good with new content and mods, but they'd have to be substantial additions. As it is right now, it's just not interesting or engaging to play.
tl;dr NMS is as wide as an ocean with the depth of a puddle.