I was a bit skeptical about purchasing this game on release as nearly all of the recent previous Total War titles have had numerous game breaking bugs upon release. And unfortunately they are still present but they are not too numerous and just mainly cause crashes back to the desktop and this is the reason fro dropping a star.
Apart from the odd crash the game is a big improvement on previous games, mainly with the AI which is far more unpredictable and aggressive. In many of the previous games once you had conquered a few provinces and established a relatively large army any AI controlled factions would not attack you, giving you free reign over the rest of the map. Whereas in this game you have to constantly be on the lookout for attacks from rival factions and revolts from within, giving a far more challenging game and one that you cannot win within a days play.
The 'tech tree' has also been reduced from the massive re-searchable technologies available in Empire and Shogun 2, meaning that by the end of the campaign it is actually possible to have fully researched your factions upgrades. And one of my main favorite features is to limit the number of armies and fleets that you can field, many would say this slows the game down and stops you from expanding. However i believe that it makes you think a lot more about attacking a new faction and opening up a new battle front, as if you over stretch your armies and expand too quick enemy factions are liable to attack unguarded territory forcing you to abandon your attacks and defend.
In conclusion this game is well worth a buy and once a few patches have been released it will be a 5 star game.