I've played some Elite Dangerous which also uses procedural generation for its galaxy, systems, and planets (but you can't land on said planets).
On the one hand, it's pretty awesome to scroll out and see all the places you could visit (but never will without a million lifetimes). On the other hand, it's pretty 'lifeless' as others have stated. I'm mostly interested in how they're going to handle planetary landings in Elite, cause that means their generation will have to generate interesting landscape and potentially cities, which is a lot harder then placing a few suns and orbits.
What worries me most about No Man's Sky is it
looks procedural. Elite Dangerous doesn't look procedural at a glance. Sure, you quickly realize there isn't a whole lot there, but NMS's planets look like My First Terrain Generator and their "galaxy" is very uniform. With Elite you get the beautiful spiral armed galaxy with tight star clusters, nebulae, and expanses of empty space, giving it a kind of "terrain" based on how far you can jump in your ship. But the brief part of NMS that I saw in Sony's presentation was just "here's a bunch of uniformly distributed stars with colored mist in the background".
So hey, I respect their achievement, but I think they need to apply some more limitations on their algorithms to try to get them to be less... 'uniform' for lack of a better word.
As to whether the game will be boring or not - that's up to the player. Some people love exploring, some people don't. There's a guy in Elite who made a name for himself by being the first to cross the entire milkyway and he documented his trip with a series of videos, so obviously he was enjoying it