I saw that a couple of friends on Steam bought
Space Engineers, and it looked interesting to me, so I thought I'd give it a try myself - And I'm glad I did.
It's a lot like
Starmade (Minecraft in space, with spaceships and little disc planets) except without the crappy retro look, with deformable blocks and much better physics, but with fewer things to do in-game at this time - Actually the two games will probably end up being quite different, so it's worth a look at both of them if you're into that kind of thing.
Space Engineers is good for an alpha though and I'm interested to see where they'll take it next.