While it doesn't look like much variety, Sean has specifically stated he's not showing much to keep everyone from knowing to much because that would ruin the wonder. It's the reason why the planets that have been shown don't have much variety. If it's truly the case and there actually is more variety than we know about this is going to be the game that revolutionizes the space exploration genre and if he's true to his word then this game will sell via word of mouth for how awesome it is.
I believe it will be an amazing game, when a developer gets up on the E3 stage and is visibly shaking it's because he genuinely cares about his game and wants it to be the best thing ever.
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It's like why the fuck does everyone need to know something about a game before it comes out, that ruins it. If it's a bad game then word of mouth will fuck it up, it's not CoD so it won't sell just because it can. You know why WoW was so amazing when it first came out? We pretty much couldn't fathom it, I loved it because I didn't know anything and led to this different kind of wonder.
Just imagine you find a planet that's fully underwater and you've never seen this before... "THIS IS FUCKING AWESOME" you say to yourself and then the next thing you find is a planet that has a primitive race of people that live in the core (center of the planet). This is why these questions are best left unanswered, it would ruin the entire point of discovery.