I read something on Reddit the other day which goes some way towards capturing my expectation about NMS. It's not particularly succinct.

http://www.reddit.com/r/truegaming/comments/28cddf/im_worrie...

That is, procedurally-generated worlds are one thing, but an engaging environment (Minecraft) or story or purpose are other things entirely.

I have a flat game concept involving procedurally-generated concept but just can't think of what might tip it over into super-engaging territory.