An excellent and addictive game for veteran Hackers as well as newbies to the series.
The game itself is pretty easy to get used to. Though there isn't much difference in most of the areas you visit, the story-line keeps you actively involved as well as entranced. Completing your item list and taking down PKers (in-game Player-Killers) can be a little tedious, but not necessary to the game. Excellent leveling system and good sense of humor. The game's most interesting feature: simulated forums and e-mailing system that lets you interact with various characters outside The World.
My only recommendation, pre-GU: watch the .Hack//Roots series. Though the game gives you a simple re-cap, you can't compare with the tv series. Also, the voices of the tv version are way better than in-game.