I am definitely noticing a few differences to other Total War games with Shogun 2. I've played about 6 hours and it's really good despite some difficulties.
I have never really liked playing the battles (which is half the game) and preferred managing from the campaign map. I went through at least 2 playthroughs on Empire and Napoleon without going into a single battle. This is not a game which you can do solely that. I'm playing on hard and reluctant to play at an easier difficulty, but the AI is super aggressive and has very large armies even at turn 3 or 4. I'm not just satisfied with having the basic Ashigaru which the AI is so keen on, and train many Samurai. This makes no difference at all to simulation. How can you update the AI without taking simulation into consideration? I think I'm going to start again and really get into the battles.
I find the starting position difficulty misleading too. I like bow infantry, so the Chosokabe clan is a clear choice. Their difficulty is easy, because you start on Shikoku, but you immediately have a hostility with one neighbor. They conveniently have an alliance with every other clan on the island, creating two fronts directed straight at my capital. Whenever I venture out to one of them (using my whole army from the problems stated above) the other sneakily jumps on my city. What gives? I started again, managing to get to around turn 60 without a war, making tons of money from trade until some clan from Kyushu randomly wanted my head via an even sneakier two pronged invasion force.
So yeah, very sneaky.