This is a good game. I've played at least 12 hours this weekend and it hasn't crashed once nor have I suffered any major slowdowns, even on a massive, 5000+ man battle defending Kyoto against two aggressors.
Units close fast. If on the defensive, once enemy melee units get in range of my archers, they will begin charging, allowing me only 2-3 volleys before I have to peel back and send melee up front. This speed makes cantabrian circle/swooping crane for horse archers less effective as well. cavalry will immediately go around for the flank. I say this specifically because in Rome TW archers and siege weapons could always do massive damage before their melee closed in. Often times I could route an AI army of comparable size with minimal losses simply because I had more archers and siege.
As for campaign play, I'm not sure what the optimum is, but after the initial 2-3 additional provinces, I tend to focus on getting as much overseas trade as possible to generate revenue, and working on getting as many trade routes and filling those routes with the most profitable trade partners. Then switch off between capturing provinces and econ, and trying best not to piss everyone off. At about 50-100 turns in, my trade revenue will be 1.5-2X greater than tax revenue, and you start to warchest. It's hard to say how big your warchest needs to be before you move on Kyoto, I think I went too little this playthrough. Anyhow, moving on Kyoto or growing too much will essentially result in the loss of all your trade partners, at the time when your army upkeep is absolutely massive. You can cushion this by raiding trade. I'm not sure the best way to circumvent this. This time I've made the provinces surrounding Kyoto that get taken along the way vassals, that way I don't have to worry as much about them being immediately retaken by enemies, since the bulk of your army will be focused on defending Kyoto from the repeated counter offensives. As an econ bonus, these vassals are automatic trade partners, so you get revenue without worrying about additional garrison units and counteroffensives.
Would like to hear some strats.