I've not played a great deal of this game, so these are just initial impressions.
To put it bluntly the game feels empty and without any structure (lack of structure may sound like a good thing in a sandbox game, but this doesn't feel like a sandbox game, more on this later). As of right now you get the sense that there is nothing you can really do in this game (largely perhaps due to the lack of population, but also due to a lack of depth).
The economics and trade side of things are also boring as you can do little more than move generic products around a 2D map, or mining asteroids (boring).
The combat has a lot of potential but against NPCs it is hardly satisfying, I have not seen any large scale PvP fights, in fact I haven't seen more than 2 other players in this game (Global chat is dead). Basic combat could be fun though as already mentioned, I just wonder if it is too "arcadey" to offer meaningful strategy.
Perhaps my largest gripe with this game is the fact that it isn't a true open universe but heavily instanced as other users have pointed out. I read these reviews before purchasing but as I do play some games that employ this method I thought perhaps it wouldn't bother me as much. However in this game it really does break immersion. Fortunately a recent trailer on IGN had them saying they plan to remove the 2D element of the game and make a real sandbox game.
Now I'm not sure where to give my advice/ things I would like to see added etc. So I'll just list them here.
-Overall much greater player control
-Real open world
-Fully player run economy with crafting (should be added soon I think)
-More depth to combat
-Much greater depth in the Cartel system, like EVE online: with departments, clear structure and complexity. Cartel vs Cartel would be awesome.
-Some Avatar combat perhaps - landing on stations and sieging stations etc
-Player or Cartel controlled structures (ability to create them), stations and territories (systems); the Cartels could get the tax from these station markets and players could fight for control over them.
-Better tutorial and more and better missions to help beginners and to add some structure to the experience.
-Player created missions, like bounties or trade missions etc.
Basically I want EVE online without all the time wasting and grinding.
This game has a lot of potential and I will keenly watch how it evolves, but as of right now I do not recommend this to others unless they want to aid in development.
This game COULD become something awesome.