I haven't actually tried Cortex Command myself yet, but it seems that there are several Steam users requesting refunds due to Steam advertising CC as a finished product, not indicating that it's still in development--which translates into a directionless campaign, lacking tutorial, and game-breaking bugs.
Here's the best articulation of these complaints I've seen so far:
Another lengthy thread:
Here's an old post by CC's creator stating that he's only in it for his own fun and profit and doesn't feel any responsibility to his customers:
Of course, there's also a team of sycophantic fans telling people the game is fine once you've installed several mods off of some forums or something.
I don't really care about CC itself (I got it for "free" through an Indie Bundle), but this has serious implications about Steam as a service. I've always trusted their quality assurance 100%. Everything I have bought, even obscure indie games, has been a complete product, exactly what I thought I was paying for. If there are known issues, it has said so on the store page (for example, the ATI driver incompatibility with Stubbs the Zombie, when it was available).
If I can no long completely trust Steam, what does this say about Greenlight? What other incomplete games will they let through?