The game is great for the early game, but it's flaws become glaring in the mid to late game-time. It has a lot of bugs and it is very unbalanced, especially in combat. The "sector" mechanic does not work well and the game events become quickly repetitive. It also has performance issues in late game.
Overall it's good and fun, but you should wait to buy it when Paradox fixes it through patches (as they promised to do) or even better, wait for the special offers. For now (19/5) the game seems like it's still in beta...
For these reason I will give it 3/5 and review it again after the 3 first free patches and see if there is an improvement.