Where I found the series start to lack, but still a good game nonetheless.
The story is disappointingly boring and uneventful, especially with the plot twist left off at the end of .hack//Mutation, where the virus spreads to the Root Towns (the hub areas) and now all of "The World" is infected. But, instead of an interesting story, the game involves a bunch of operations that are boring and involve no plot twists and mystery, which is a great part of the franchise.
The gameplay isn't helping either. The game now has found a brand new love of tolerances (the games immunities), where almost all of the monsters have some sort of tolerance, which if not for certain items (which actually turn out to be common, thank goodness), would be very annoying and hard. Data Bugs are now common enemies in some areas, and while it can be cool, it can also be annoying in dungeons, as you must beat them to go on, and the Data Drains used to return them to normal increase your infection percentage and when that reaches 100%, you get a game over. That little nuisance leads to many close calls and prevents from getting all the treasure and opening all the dungeon portals.
Luckily, this game improves on the easter eggs, having many more than the last installment, including phantoms of .hack//SIGN characters that wander the Root Towns and the chance to free Sora from Skeith's wand.
Unfortunately, this game is the worst installment of the first three. It has it's pros, but too many cons, including the well-known repetitiveness.