Well, I just got it and have only started playing around with it a little this morning. I’m playing a short campaign on N/H with France to unlock the factions and acclimatize myself. Probably I’ll set at H/VH for full campaigns ( the strategic AI’s frequent hyper-aggressiveness when set to VH just seems ridiculous and takes me out of the role-playing aspect ). Supposedly instead of higher battle difficulties just affecting morale, fatigue, etc., it still effects those things, but effects both the player and AI equally, with the AI scaling up in ability. Haven’t tested that, but it’ll be a big improvement if true.
So far I’ve fought very few open field engagements, none against an equal opponent ( all were bandit mop-ups ) and no assaults. In general it’s not part of my game plan to assault unless really pressed for time ( i.e. have to take a town and dig in before a much larger column arrives to drive me off ), which I find tedious. So almost all my battlefield experience with the game has been on the tail end of sieges when the starving garrisons have sortied ( at Rennes, Bourdeaux, Metz, Dijon and Antwerp ), which isn’t a terribly fair test of the AI. I’ve only just started my first war with an actual faction ( those feelthy Norman dogs of course 
) and those tea-drinking wusses have withdrawn their full stack to Caen, rather than meet my full stack in the open. I’m not sure whether to siege to get this initial game over with ( gotta unlock ) or try to draw them out. But anyway…
It sure is pretty. And I’m not even at the absolute highest setting. I particularly like the new high-arcing archery animation.
The tactical AI is, so far, no worse than BI-level RTW ( which would indeed try to flank with calvary ) and possibly a cut better. But it will take more testing to suss out, especially in the open and on VH. Command units do still tend to recklessly charge at times, albeit it in a reasonably cohesive faction and often to flank or at least at a gap. But that bother me a little less in a medieval game, when such foolishness was the norm. Also that may be a function of being frequently outnumbered. I’ll occasionally roleplay a little recklessness myself, depending on the character.
The toughest fight so far was Antwerp, which I stole with a scratch force after the large rebel garrison repelled in succession two German and one Danish assault. In that one I was slightly outnumbered ( and they didn’t wait to get starved, they properly sortied immediately on the first turnwhile they still held that advantage ), they had more and better heavy infantry and more heavy calvary, while I had a unit of light calvary they lacked and a small advantage in missle troops ( but it was pouring rain ). I lost every single man in my single spear unit and suffered heavy casualties to my calvary, but won by repeatedly sandwhiching individual units between my light calvary and heavy body guards and then retreating before I could get swarmed. Also I had a good commander who managed to survive, while theirs went down early.
A known issue, which apparently CA owned up to pretty much simultaneously with the games release. It’s a “passive AI” bug that sneaked in when the game was going gold. It’s apparently #1 on the list of items to be addressed with the first CA patch which is due in about two weeks.
This is no longer 100% true ( though it largely is ) with the implementation of the new merchant/resource system. Which frankly I’m not crazy about. It seems bugged or else just plain unbalanced - stealing resources from other merchants ( which means losing a 550 florin unit every time ) seems to happen wayyyy too frequently. It’s clumsy in implementation if you ask me and with the current imbalance, pricey and a micromanagement pain in the ass to boot. It needs to addressed IMHO.
There is also a seeming issue with calvary orders. Not a problem with a little more micromanagement, but they don’t always charge properly with a double-click, instead often sauntering up at a canter to engage in hand-to-hand ( the AI doesn’t have this issue far as I can tell ). For those who don’t like to pause ( I’m not one of them ) it might be pretty frustrating.
Hell, I was playing Rome TW until last month, and thats been out since 2004.