A month old now, so possibly time for a bit of a review. I haven't mentioned any of the broken / not implemented yet stuff for obvious reasons.
The good: the battles, especially the combat part of the sieges and big fights. AI in fights is much improved, with both sides using tactics that make sense, and people running off based on their experience. Upskilling your army seems a lot better in this than in Warband (where you could just have high training and then they'd be top tier in a few weeks). There is far better balance between cavalry and infantry / ranged (and different tiers) in this than its predecessor too. Best of all is the attention they've paid to fighting itself, which has taken an already great system and made it even more intuitive (and occasionally spectacular) - chasing fleeing enemies through a wood and accidentally hitting a tree whilst you swing at them is oddly brilliant.
The bad: the map is far too busy in terms of terrain features - it looks fantastic, but a little less mountains and more farmlands etc would not go amiss. Caravans take stupid routes during wartime, and need to avoid combat areas entirely after a while. The various mercenary companies are a great idea but they are (at the moment) no better than the regular forces, and often much worse. The "main" storyline is rubbish - they'd be better off ditching it entirely whilst giving you a choice of starting location and race, but with the options available in that land (eg: Battanian starts in the Empire would be people of outcast status, and so on). I'd also like to see the post-battle looting take time rather than just dole out X amount of items straight away - you should be able to spend ages looting the corpses and getting more out of it (whilst risking their mates turn up).
I know its early access but if they'd released the full version in this state, I'd still love it to bits.