I will write a full review of the full game, but for now all I have is the demo and a Custom Battle mod.

The demo gievs you a tutorial campaign, and a historical battle. I first dove into the campaign to see what new stuff I have to play around with. The last Total War campaign I really played a lot of was Medieval 2, so I was interested in seeing what all they have added and removed.

It first goes over the basics, showing you how to move your guys, merge armies, etc. It shows you how to train units and build buildings, along with adjust the tax rates and all the ordinary stuff. Nothing too drastic, but the campaign gives you some battles to fight, but not with the units you have created, a set of units they picked out for each fight. If you quit a battle, you automatically win it (as I discovered when my first siege attempt went to hell).

The first is less a battle and more of a tutorial. You follow a step-by-step guide which tells you how to move your units about and their special abilities. You move your Yari Ashigari (peasant spearmen) down a hill, resist a cavalry charge with a spear wall, then regroup with some archers. Then you get some horsemen and after some murder making, its back to the campaign map.

The 2nd fight you get to fight is at a village. The goal of this battle is to take out an enemy commander and take control of the village. You take out small pockets of enemies as you go along, with some hidden until you get to a certain point. Once you make it to the general, his whole posse comes and has a go at you. You take them out and back to the campain map.

The final battle is a castle siege. You get some cannons, some ninjas, and a hero unit of bowmen (smaller unit of uberly awesome guys) to play around with (along with regular units). You just gotta take the castle, driving the enemy to the keep. The only difference between Shogun 2 and Medieval 2 is the castles are multilayered and there are more things to capture along the way. Stand in a circle next to a tower long enough and the towers weapons will kill the enemy's dudes instead of your own. Capture the keep in the center or destroy all enemy to win.

The historical battle is the Battle of Sekigahara. During the fight, one of your teammates turns on you and tries to kill your guys. The best strategy I found was to be defensive and hold the high ground. I started the fight by moving my guys to the high ground and massing my cavalry. The AI disappointed me when it sent all of its cavalry forward and let me murder it. It also left its ranged units unprotected for the most part, allowing my cavalry to murder them too. Your army starts split, and while I was concentrating on 1 area, the other side was being neglected. The neglected side looked like it was going to fall during one of my check-ups on them, but the loyal ally's men saved mine.
 

After defeating the real enemies army, the betrayal happened. I took my cavalry to take down the real enemy general and they were hit in the rear by the betraying general. I was able to send the enemy general packing and got my guys away from the betraying spearmen. The betrayers were dead set on killing my cavalry, and I led the betraying general far enough away from his army to defeat them (with help from the surviving spearmen on the neglected side, who I was moving to rejoin the rest of my army along with the 2 bowmen units). I then brought those men back to the main hill and set my men up to resist the enemy army. Spears and swords on the front, bowmen behind. The enemy units were exhausted from chasing my cavalry while most of my guys were rested. Despite being outnumbered, my men were able to crush them. 1 enemy Naginata Samurai unit tried to outflank me, but was shot the hell by my bowmen who then scared the survivors off with a charge (4 slightly depleted bowmen right next to their army and general vs 1 depleted and exhausted samurai unit who had no allies and a general who ran away). Victory was mine, but only by a narrow margin.

In conclusion: The AI in the historical battle was a little off at times, but it did far better than the AI in Empire and Napoleon. The campaign is simplified, but limits how much stuff you can build in 1 city. The battles are like M2 and Empire had a baby and I really really like how routed enemies' morale is broken or shattered (broken may return, shattered will not), which stops my biggest complaint with AI units in Rome and M2 ALWAYS returning far more often than your units will after being routed and not pursued. Download the dmeo off Steam and try it for yourself.