I've finished a campaign as Cimmeria (sp?). First time I've spent more than 2-3 hours with a Total War game since Medieval 2 (and I didn't even play Rome 1 at all). It's still the popamole of grand strategies it always was, the "free movement" 3d strategic map just makes it more tedious. Some of the mechanics are completely fucking dumb and seemingly designed with the intention of pissing the player off as much as possible. I still had some decent fun with it though, nice graphics and murdering barbarian hordes with ballistae and hoplites is satisfying.
The province development is the biggest culprit here. I don't even mean the fact that it looks and feels like something taken out of a flash game, but the "build stuff that gives food and decreases happiness, build stuff that gives happiness but uses food" mechanic it's based on, jesus. When you have more than a few provinces and you research something new you can't even build it, you have to count how much food it will use up and usually it will use up enough to put you on a negative. Since the game doesn't give any warning of "you gonna starve bro" I lost a war first time it happened since negative food decimated my best army from full strength to like 10 men per unit in a few turns. Even worse, those penalties that buildings carry with them don't even make any sense most of the time. OK, military buildings use up some food and working in an ancient mine probably sucks so I get happiness penalty, I can buy that. But why the hell does building farms make my population unhappy, with butthurt progressing as I modernise and upgrade them? Resistance to frankenwheat? I'm no expert, but I'm pretty sure ancient Greeks didn't rebel because someone was trying to feed them. And an example from the other side: constructing sanitary buildings apparently puts a huge dent in my food production. Seriously? If there's one thing worse than dumb and irritating game mechanic it's a dumb and irritating game mechanic that's also completely arbitrary. Oh, and people rebelling because I just conquered an enemy town in the same province. Hard to fathom someone dumb enough to think that the global happiness thingy from CiV was actually a good idea.
The interface takes the second spot. You thought that Witcher 2 or post-Morrowind Bethesda games had an abortion of a UI? Well, those games were console popamole action dross, this here is a PC-exclusive grand strategy game and yes, it's worse. The research tree takes 6 screens instead of one for no reason whatsoever. You think maybe with these huge-ass technology icons you can at least see all the details on what things do on a given screen? Nope, six screens and you still have to hover over each one individually to know what it is and how long it takes. But brace your undies for the general and agent skill trees. They exist, but you can't see them! Yep, before you learn them by heart (sic!), you have to consult the unwieldy encyclopedia/manual every time. Want to upgrade your 20-unit army with new armour? Hovering each unit once for selection and clicking once for actual upgrade sounds fun, right? I will admit though, I'm not sure why people were making so much fuss over the unit cards or the battle interface. These seem pretty clear to me.
The third goes to the hard limit of armies and the requirement for each of them to be led by a magically spawned general. This makes logistics and army management tedious, especially reinforcing/modernising your line stacks. And generals respawning each turn from thin air is just pants on head retarded. Killing/assassinating an enemy leader often works against you because next turn you'll have to face a full strength unit of elite troops.
Battles are OK. Typically for this series they are incredibly easy and you have to be facing really overwhelming numerical/technological (and the second almost never happens) superiority to not win with like 3-5:1 kill ratio. AI is predictable and suffers from occasional brainfarts, like running their cavalry in pointless circles or suddenly stopping its troops under heavy fire, but it often tries to flank and uses skirmish/missile troops pretty well. Its cavalry charges also took me by surprise a few times in bigger battles when there's lots of stuff to pay attention to. Unit collision is pretty bad, yeah, looks really weird sometimes, but I like the general feel of combat, raining fire on approaching barbarian hordes feels good man. Naval battles... I'm not sure I understand them. Sometimes I order all my ships to ram and they sink enemy fleet instantly, but sometimes the ramming doesn't seem to work and my ships get boarded on contact and boarding is magical and can't be disengaged, AI loves to use fleets composed of actual land troops and they are much better at boarding than regular navy, go figure.
Later on of course you autoresolve most stuff, even though the autoresolve is hilariously skewed (another revered TW tradition), predicting total army loss in battles that you can win blindfolded and massacring your siege weapons and cavalry no matter the odds.
The strategic AI is both bad and good. Bad, cause it nags you with "gib money" all the time and morons refuse mutually lucrative trading agreements even if you offer 200k gold in a bundle (literally, I tried that). Good, because it doesn't go berserk on you for no reason or when it has 0 chance of winning and it actually does recognize when it's beaten, even offering tribute or becoming a client state. So obvious, yet so few strategy games have that. I think it still cheats, though, one-town factions produce and support full stacks of units which should not be possible and I think they still spawn armies out of thin air where the player can't see it.
Finishing a campaign also takes way too much time for the kind of entertainment this game provides. Initial struggle is exciting, grinding for the victory objectives is not. Military requires you to take regions across the whole map and maintain 240 units afair, which is a crazy amount (you don't even need half of that to take on anyone on the map and win comfortably). Economic needs trading agreements with 15 factions and an income of 90k net per turn. That's the one I won, but those requirements are rather mutually exclusive, by the time you expand enough to earn that kind of money there are barely 15 nations on the map and most of them hate you for expansionism. Cultural - don't have any thoughts about that one, but conquering provinces and switching them to your culture is probably similarly grindy.
Performance wise it seems fixed, at least I see no problems. I can run it on very high just fine on my laptop, better than Shogun 2 actually, at least the loading times are much faster.
Edit: Oh, and I ignored the political stuff completely. Seems pretty tacked on to be honest.