Hideo Nakata's follow-up to "Ring" is terrifying stuff. Building on the events of the first film and following the dreadful video curse through to the next level, it is a very worthy successor to the original classic.
In terms of filmmaking style, very little has changed. "Ring 2" is high quality horror filmmaking, including excellent music, a couple of nasty shocks (used sparingly, making them all the more effective) and some really frightening images which stay in your mind long after the film is over. We also learn more about Sadako and the circumstances leading up to her imprisonment and death, which deepens the horror by making the audience more compassionate towards the object of fear. This is the sort of thing that classic Western horror USED to do, but now it is more concerned with shock tactics and tongue-in-cheek self-referencing (see "Scream") to bother with good old-fashioned empathy.
This is not to say that we grow to love Sadako any more in this film than in the first. She is still very much the epitome of evil. "Ring 2" also makes less sense than its predecessor and demands more leaps of the imagination than the first film did. That said, the irrationality leads to some truly terrifying moments: the way the curse marks all media (photos, videos, any TV in range); the whole sequence with the well; the flashback sequence at the Inn where Sadako was raised. By not trying to be too logical about the plot here, Nakata actually taps into a deeper vein of horror, although it makes "Ring 2" slightly less satisfying than its predecessor.
Everything about this production is so good that it barely even needs to be mentioned. The acting is terrific, particularly Miki Nakatini as Mai, burdened with a psychic capacity she doesn't want and drawn into the mystery against her will. Rikiya Otaka also deserves a mention as Yoichi (the little boy from the first film) - his expressions of blank terror and occasional moments of rage are very effective indeed.
Don't watch "Ring 2" alone and don't expect to sleep easy afterwards. This is good quality horror the way it hasn't been made in Hollywood for a good few years now - go with a friend!