After having finished the Wei storyline, roughly half of the Wu storyline, and messed around in Conquest Mode for a couple of hours, I have this to say.
 
Dynasty Warriors 7 is the best game in the series.
 
No, seriously.  Just about every change made is meaningful and adds more depth, complexity, style, and detail to nearly every facet of the game.  They threw out the Renbu combat system and went back to the old tried and true, then added multiple weapons and weapon switching attacks, revamped the musou gauge and the way musou attacks work, the character upgrade system is a mix of permanent stat-boosting items, skill points, and weapon abilities, and beyond a few standard stages (Yellow Turban Rebellion, Dong Zhuo's insurrection, Battle of Chibi), the campaigns feel completely fresh.
 
And a lot of that freshness has to do with the way that the game's story mode is structured.  In story mode, there's no character selection; the character is predetermined by whatever the current stage is.  So there's no magically weird story that follows a single character for over eighty years and don't necessarily end with their respective kingdom winning out and unifying China.  If anything, this game is more faithful to the original text of Romance of the Three Kingdoms than any of the Dynasty Warriors games before it, though it still takes numerous liberties for the sake of gameplay and dramatic license.  They even included the kingdom of Jin, which in the text and historically ended up growing out of the three kingdoms to establish the next Chinese dynasty.
 
So no, you don't play as everyone in story mode, but the Conquest Mode lets you play as anyone you've unlocked.  It's basically a challenge mode comprised of different stages, including challenge battles for specific characters, many of which are based on events from the novel that aren't covered in the story mode.  Then there are the smaller touches, like the fact that the English localization is easily the series' best; it seems that they went out of their way to ensure that most if not all of the Chinese names are pronounced properly this time around, and there are small graphic touches, as well, such as Xiahou Dun actually having a character model with two eyes and no eye patch prior to the point he gets an arrow shot in his face.
 
So while I'm sure that none of this will be of interest to those that enjoy using the series as a punching bag, this is plenty of extra incentive for people that enjoyed the previous games to give this one a go, too.