I figured I'd ask a roundup of questions that I had on some differences between GC3 and GC2. I just purchased 3 earlier this week and just now jumped into it.
- I have noticed that I am unable to build anything but the first 'tier' planetary improvement (factory, research lab, etc) Is this working as intended, because in 2 you were able to build the highest tier improvement you had researched at the time, regardless of there being an earlier tier improvement on the planet.
- What is the 'sweet spot' for galaxy setup with respect to having enough habitable planets while not having too many?
- How does mining asteroids work in the game now? Am I missing an option in my shipyard to build a mining ship like was in earlier versions?
1. Technically. I hate it as do many others and it is a hindrance to growth. (And is annoying.)
2. Abundant everything will give you a full galaxy. Not sure how it scales percentagly for each setting per map size so just push some buttons and see what you get!
3. it's a line of techs in the engineering branch that unlock mining of various types.
As for new features, not like I'm counting...:
1. Hex style map.
2. Shipyards
3. 100 race maps
4. 64bit
5. Drastically improved ship designer.
6. Overhauled morale system.
7. Ideology trees.
8. In depth combat simulation for dynamic battle outcomes.
9. More diplomacy options and strategies.
10 tech ages. (Sorta hate them though)
11. Tech specializations.
12. Space pirates.
13. Carriers.
14. More customizable races and modding.
15. Interactive space objects like black holes and nebula.
16. Reimaginged resources and space relics.
17. Planet traits.
18. Improvement adjacency bonuses.
19. Multilayer games.
20. Augmented weapons and ship components.
21. Soon to come expansions that will overhaul espionage and ship leveling.
I hope that is enough to constitute buying the game and not think of it as galciv 2.0 like some people do. 
1. Hex style map. Is really great!
2. Shipyards, become a production bottleneck because you can never build more than one ship per yard and never more than one yard per planet in your empire, well you can but you can't do any production on them unless you micro the hell out of it.
3. 100 race maps Only its really 89 major races + 8 minors and 1 human, so yeah not 100, not 128, but still big.
4. 64bit, but the game drags ass like it was coded to run on 32bit but runs on 64bit reluctantly.
5. Drastically improved ship designer, wasn't much wrong with the original ship designer, now with more flash.
6. Overhauled morale system, except it is completely busted to hell.
7. Ideology trees, which are imbalanced as all get out.
8. In depth combat simulation for dynamic battle outcomes, LOL yeah right. You watch and hope your ships don't do something stupid.
9. More diplomacy options and strategies, Diplomacy is completely busted, lags the game, is annoying, and easily one of the bigger problems with the game because it is a free windows into every ship or station or planet, tech, amount of cash on hand the enemy has.
10 tech ages. (Sorta hate them though), not a terrible feature, but only 3 of them, and what is the point of them?
11. Tech specializations. Pretty cool, and you can trade for what you don't have, so you don't really need to research anything if you don't want to.
12. Space pirates. That lag the game.
13. Carriers. Which are so overpowered and imbalanced as to wreck all space combat, why build anything else?
14. More customizable races and modding, Very customizable, modding needs love from SD, but the game is very customizable, almost too much so.
15. Interactive space objects like black holes and nebula. Not very interactive but they exist for variety.
16. Reimaginged resources and space relics. Isn't this 15? Anyway yeah, they re-imagined it, too bad it isn't really better.
17. Planet traits. Cool
18. Improvement adjacency bonuses. Very cool, but still no documentation on how it works anywhere.
19. Multilayer games. Pretty cool, but sorta late to the franchise, because they went this route now everything will have to be balanced for SP and MP.
20. Augmented weapons and ship components. Prototype ships are cool, everything else is imbalanced fluff.
21. Soon to come expansions that will overhaul espionage and ship leveling. Yeah after a good year of bug fixing. We can welcome expansions.
