A finely tuned blend of the old and the new - Shogun 2 is Bushido perfection.
One great improvement is the AI (on hard) is just a lot smarter, and behaves more tactically, almost like a human being would to exploit your weaknesses, and gets you starting new campaigns a lot, a good sign!
All aspects of other total war games are here, the great combat, the strategic map - in a weird way Shogun 2 feels like it's so much deeper. You can recruit monks who are able to sub-vert and incite other cities to revolt, so you never have to declare war but can fight by proxy.
The use of alliances seems more realistic now, i've been allies with one clan for at least 30 turns, but based on their "integrity" trait, they are less likely to stab me in the back.
A lot of these nuances makes the game so believable at the strategic level, I understand why going back to Shogun made so much sense, because in a smaller scope, ironically you could bring more depth to the game.
If you haven't gotten this game yet, don't wait...