I bought this game as I had previously enjoyed the Rome total war Gold Edition as well as the Medieval 2 Gold Edition. The graphics are definitely a great improvement and the battlefield looks great. The battle animations are also much more exciting making saved replays a lot more entertaining to watch. Unit variation is no way near as rich as Rome, but i guess its a historical limitation. The AI has vastly improved from just sitting round and letting u shoot it to pieces. Diplomacy is much more fun now as the AI is much more active in attacking each other, declaring alliances or offering trade deals. Anyhow, The naval battles are pretty boring, there's nearly no opportunity for strategy. What tends to happen in campaign is that the computer bunches up all its ships in to massive fleets and when u fight them its just a big, random mess.
BUT the biggest problem with this game is actually being able to play it! I bought the game in CD about 6 months after release to avoid bugs and had to install Steam to play it (ugh). It took me 2 days to figure it out. My computer had well over the minimum requirements and after installing it from Steam (which took like 2 hours) i would click "Play game" and after a few secs my screen would go black and crash the computer. It did this time after time. I did everything Steam Support had to say but nothing would change. Well, in the end it turns out that Shogun 2 Total War conflicts with Realtek HD audio, so i had to change it and voila it worked.
In summary, great game had a lot of fun with it. But Creative Assembly, you s*** at testing.