If you're a big fan of the Dynasty Warriors, Samurai Warrior or even the previous Warriors Orochi games, you'll love this one, it has all the good elements of the massive series, or if you've even never played any of these games, it will be an excellent starting point.
Koei normally loosely base these games on historical events (Three Kingdoms era for Dynasty Warriors and Senkogu period for Samurai Warriors) but they have really let loose with this game, introducing characters from other titles, such as Ryu Hayabusa (Ninja Gaiden titles), Achilles (from Legends of Troy), Joan of Arc (from Bladestorm), Ayane (Dead or Alive 4?) and Nemea (Trinity: Souls of Zill O'll) as well as a host of others, meaning there are a whopping 132 playable characters to choose from!
The story of the game puts you right in the thick of it to start off, by everyone being killed by the Hydra, and you needing to travel back in time to help save all of your friends to even have a hope of defeating it.
Koei introduced a new feature in this game, being able to customize and share your own "Mosou Battlefield", as you complete stages you'll be able to customize them in your own way, as you play that level, you'll unlock "edit points" to add in more soldiers, or different sound effects and such. I personally never checked out this feature because I had no interest in sharing or replaying any battles it hadn't already made me replay.
The "town" feature from Dynasty Warriors 7 and Strike force has been kept, where you can purchase new weapons for your characters, host a tea-party to increase "bond" with other warriors (Which can be insanely confusing at first, if you switch characters)
The way the level select is laid out is all over the place, you must build up bonds between certain officers to unlock certain bonus stages, which will change a certain battle to "redux" and there will be a different outcome. This feature, in my opinion, by the third chapter becomes increasingly annoying, having to re-do certain levels, it begins to feel extremely tedious.
Graphically, the game as changed quite a bit over the years, it's not quite a beautiful looking game, but I think that is part of it's charm, it doesn't need graphics to carry it. Each character now has 2 new costumes added, at first I was confused seeing some characters as they had changed quite significantly, but for the most part they characters look excellent as always.
In Dynasty Warriors 7, they added a feature where any warrior could wield any weapon, and at first I found this to be an excellent idea, but then realized there would be no reason to swap officers, and I think Koei realized this as well, the characters are back to wielding their traditional weapons (Ma Chao; a spear, Lu Bu; a halberd)
The Achievements for this game aren't exactly easy, but I wouldn't say they were difficult, if you're buying this game for the hope of an easy 1000Gs I think you'd be best to look elsewhere.
I absolutely LOVE Dynasty Warriors, Warriors Orochi and Samurai Warriors, I own every single one of them (Minus DW1, and SW3) and I find this game to be amazing, probably the best that the entire "Warriors" series has to offer, I enjoyed the story, I liked the characters, I even liked how the integrated other game characters into it, but even for all the love I have with this series, I found after a few hours of solid X button (Xbox) bashing and adding in a few presses of Y during an officer battle, even I got bored of this monotonous labor.
It is an excellent game and well worth checking out, despite it's hindrance in graphics toward most modern games, and somewhat monotonous button bashing, you will enjoy it if you're a fan of the series. I hope you found this helpful.