I have been a backer pretty much since day one. Refrained from playing until recently, due to performance issues and wipes.
It's a very ambitious game, so much is clear. At this point very much a gather, craft and build game still. There are no NPC's; everything is player driven.
If you have played Space Engineers, you'll know what to expect. It's basically that on steroids with large scale multiplayer and even empire management (when your player corp grows large) built in.
It's as free and probably will become as brutal as EVE online down the line, I expect.
The draw for me is that its very simulationalist with its systems and atmospheric model. Dynamic weather is planned as well.
Ships (called dynamic constructs) and bases (called static constructs) are built out of functional blocks and voxels. The damage system provides for per-voxel damage modelling.
The fact that its one big persistent universe is super cool as well.
It also features real time offline skill training, like EVE. And the skilltree is HUGE.
The grind is pretty real though. My personal experience has been pretty frustrating so far with getting started. You'll need a scanner (which has low range due to lacking skills) to mindlessly wander around the surface to hunt for returns. You'll then need to pinpoint the resource vein and can start to dig.
But you won't know beforehand which resource you'll find, just its Tier.
This makes getting started very time consuming imo and should be changed. Or, perhaps I am just doing things the wrong way.
Add me in game, Justin! (Cyriac Daventria)