Alright, so after some more time put into it, and since some people here still seemed on the fence, I decided to write up a more comprehensive summary
Overall, it is a very nice game, a mix of 4x and grand strategy, with well designed economy and warfare, (almost) seamless FoG2 tactical battles implementation and some problems in diplomacy and AI department, but it is far beyond anything that Paradox has recently done
+ Building system, economy and trade - this is a highlight of the game and it is hard to divide it into categories, because of how closely all the systems play together. Firstly, they advertised to have about 400 building types and that seems like it is true. Now, most of the provide You with some basic resources of which there are 2 types - in short - state and provincial ones. Within the province it is: food, infrastructure (essentially production for the purpose of building buildings), health (supplements growth alongside food), culture (counteracts decadence - more on that later) and equipment (production for units); as for state level: Gold, manpower, metal and legacy (score and also determines your civ level along with decadence). As You can see there are quite a few, however it isn't just as simple to build as many to get as many of all resources, because of the trade good system
Many buildings require specific materials to operate. If so, said good is automatically imported to allow the building to work (For example salthouse needs salt) if it is available within the trading range. So far it is simple, but most buildings require also 'bonus' trade goods. They give hefty resource bonuses for satysfying their trade requirements, however bonus goods do not get imported automatically (they are used if the good is present in any of adjacent provinces or is imported by some other building to the province). Now the catch is there are a lot more buildings that give bonuses for bonus goods than those that need those good and actually create demand. And it is the bonus goods that make your buildings real moneymakers (some even require them to be any profitable). This makes for a really interesting economy where You actually have to think what to build. It is only made better by the fact that building options are randomized so it is really hard to min-max. Adding to that, some buildings have special traits like giving bonuses to recruitment, taxation, garrison strength etc.
+ Warfare - for a grand strategy the military layer is rather well done. There are about 6-10 unit types per faction and every reqion You conquer has its own provincial units (although many are similar to each other). The auto-resolve battle system is good, and unlike the game contenders it doesn't just boil down to dice rolls. The more experienced Your units are, the higher is the threshold below which a dice gets re-rolled, the better Your general, the more dice You roll and pick the highest number. In short, the better Your troops and command, the more *reliable* Your army gets. This is a nice dynamic. Of course, there are also many terrain modifiers that differentiate effectiveness of your troops as well as frontage system.
The auto-resolve is good, but warfare is made great by the FoG2 integration. As far as the infrastructure goes, changing between games takes a couple clicks and is extremely fast. The fact that it is not within one game is no issue at all. FoG2 battles are just great, and the units transfer over from the campaign pretty well (from what I've seen, everything: terrain, general skills, unit experience and frontage is taken into account). There are however some minor problems. Naturally if You play the battles manually You get advantage over the AI, also because of how FoG2 takes into account desertions and capture, their outcome is usually quite one sided. Also, Your casualties tend to spread over Your units pretty evenly, so it is much much easier to keep Your soldiers around than with auto-resolve (side note: Naval battles and siege assaults can only get auto-resolved)
+ The depiction of age and nations - is rather good. Nations feel and play differently, due to different unit rosters, modifiers (nation specific or dependent on political system) and buildings. There are also numerous world wonders and faction specific mechanics. For example Carthage has to rely on mercenaries because of its low manpower (but gets some bonuses for that), Diadochi empires, if they get in trouble get divided among neighbours. Everything seems well researched and put together. Along with that, there are special decisions - they usually give some option to exchange resources, raise loyalty, gather mercenaries from surrounding tribes, etc.
Furthermore, there are differences between regions, not only they provide regional troops (need good archers? - go to Crete) but also some buildings are region dependent - for example crops related - You can't build a winery in the far north or south
+/- Legacy and Decadence - this is a system that governs Your civilization progress. the devs seem very proud of it, but it is very simple. Basically expansion and having certain buildings raise Your decadence. To counteract it You have to produce culture. When You have a culture deficit for a longer period of time, You country stagnates and deteriorates (and can spawn a civil war). If You produce way more, You advance. Depending on the situation, it can be very easy (in my experience playing Macedonia) to keep it high, or almost impossible (as Carthage). It is nice and is certainly a good system to force a player to slow the expansion, also gives smaller nations some edge. How it plays in the long run however I would have to see over the course of more games.
- Diplomacy - very barebones. You have some basic options, but their usefulness is rather questionable. There is cooperation, that gives some trading rights and raises disposition over time, but I was attacked by nations I was cooperating with more times than i can count. Also, AI really likes attacking You out of nowhere. This would be fine, but when suing for peace You have no other option than to stop the war at the current state - there is no vassalizing, contributions, region trading. You have to either beat them (and get the decadence penalty for regions You don't even want) or to stall and just defend until they get bored and agree for peace
- AI - I am not sure if it is all that bad, since it can be challenging (especially if when as Carthage all the desert nations decide to swarm You) but it makes weird decisions. To give an example, as Macedonia I hold all Greece but Athens. They hold only that region, yet decided to go to war with me. I had no armies around, but they did not send their forces (although my fortresses might have been just to strong for them). While it might be a decent representation of Athenian foreign policy in the 3rd century BC, it was a retarded move that they gain nothing from. Not only that, I gave them money about 4 turns before because i wanted to enter cooperation (that they did not agree to). I might need more time to judge AI as a whole, but it is certainly a controversial spot.
- UI - It is between meagre to terribad. Unit and building descriptions are decently done, but they could provide some more information (for example if they produce a resource - what this resource can be use for, or if any place in range wants to buy it). The decisions I mentioned before are the worst example, since they give You no relevant information whatsoever - if You recruit mercenaries, no info on amount or quality; if doing a religious feast, they explain what the decision does, but then You have to check manually which regions have required buildings for it to take effect (no tooltip whatsoever). I like how the UI looks graphically though.
Phew... I hope it will be of use to any of You