For me GalCiv 2 was ideal in everything except of battles. So, in GalCiv 3 is nothing worth to buy it as a new game. At some moment it is worse then Twilight of Arnor.
Well, now we're into personal taste. But I would say that as a fan of GC II, GC III is a MUCH better game already in its current state. The only thing I personally miss is being able to spy on planets, but that's coming eventually. Or some sort of espionage system at least.
In fact, I'm pretty sure that the only things that TotA had (which, I will remind was two expansions past the base game) that GC III as currently stands is the espionage system and ship experiernce points. The only other thing missing is some of the major races, but, AIUI, they will eventually number to 16 over the lifespan of the game. Which will be more than GC II had at End of Life.
For me, GC III is SO much better already than GC II, that I find complaints that it hasn't changed much to be curious at best.