I really dislike the Steam review system, but given its limitations I have to say DO NOT BUY THIS GAME...in it's current state (1.12?). It is very buggy still and there are some aspects that the devs have said will be addressed in coming major updates (or maybe DLC) such as the horrible starbase management and planetary invasions. Until those are implemented I'd say new players would be better to not buy this game.
The game was released too early and post release it has had patches, but the quality of that support has been quite low. Given the past performance of Stardock I have to assume that the reason behind the poor state of the game is that Stardock put its focus on the other game they are working on (which was just released when I wrote this) The Sorcerer King.
As a business decision you can understand why they would put more focus on a new IP over fully supporting a established franchise that has already had very strong sales pre-launch. GC3 is more of a sure thing in sales, Sorcerer King is not and is more dependent on great reviews to drive sales when it is at its highest price point. So that means they have to take advantage of the established GC fanbase, which is more likely to let them get away with something that is ethically a bit dicey. I can understand them doing this (if they have. This is all just my opinion of what's going on), but it doesn't mean I have to like it.
On that note I've not been a great fan of how they are dealing with DLC. They had essentially Day 1 DLC that was infinitely exclusive where they have stated it will never be offered to anyone again. Then their first paid DLC is wrapped around the map editor. Very disappointing moves by Stardock, though I don't really rate it as a major thing on whether to recommend this game at this point in time, rather it's just something the should be noted.
There are some good aspect to this game. The shipbuilding is a star feature. It is generally superior to that offered in GC2, though I'd say it might not be as user friendly as in GC2 (be aware my views of this are very coloured by GC2 after two expansions). Graphically it looks pretty good, even on a pretty average system. The events and whatnot are entertaining and the game still has that sense of humour of the previous games.
Now this is why I have a problem with the Steam rating system. I enjoy this game. I have fun with it, mostly through the ship builder and the more lighthearted aspects of the game. However, I can't ignore the bugs and that some features are waiting to be fully dealt with. If I could I'd just give it a 6/10, but with Steam it's either a 0 or a 10 and I feel that 0 is probably fairer than 10 at this point in time. Until that happens, which going by the devs statements is maybe 3 - 6 months away, it would be best to hold off buying the game.