It's been a few months since I saw this film, but what I have to say doesn't need that many details. First of all, I'm a pretty big horror fan, but I can't totally get into the Asian horror film scene of the last decade or so. Sure, there are a number of great films that I've seen, (Cure, Audition, Tale of Two Sisters, Uzumaki) but I find it tough to come up with too much enthusiasm for seeing that many more films from the the period. The movement seems to basically be a combination of generic girl-ghost and a number of oddball horror/exploitation films that don't fit into any particular subgenre, or sound particularly thrilling to me. This is one of those generic girl-ghost ones. It's pretty well done, nicely shot and whatnot, much slicker than say Ringu or Ju-On or the original Dark Water but I don't think this subgenre needs to be endlessly repeated. I don't actually have anything against the girl-ghost movie in and of itself, but it's too narrow to allow for excess repetition. This expands out a little, reminding me of 'Stir of Echoes' and 'What Lies Beneath', but that's not really that far to go. (One might suppose this is quite derivative of the latter, but the similar plot developments in each film are insufficiently novel for me to assume that this is the case.) It's moderately scary at the beginning, but it tends toward overkill, as we see the ghost again and again in a very short timespan. (The opening scene is very good, the best of the movie, which is pretty much always a bad sign.) Then, when we get to unravelling the mystery the whole things slows down a lot and is quite a bit more low-key, and a lot less tense. Also the whole tech-horror aspect doesn't really work for me. Like others, I'm not especially terrified of the telephone. Frankly, Ringu and The Ring worked in spite of the technological element, rather than because of them. I find it tough to imagine that I'm the only one who was initially hesitant about those films because they were about cursed videotapes. But, whatever.
If you're a fan of the genre you definitely ought to see this. It's pretty well done. But, if you don't feel any particular need to see another girl-ghost movie, there's no strong reason why you should make an exception for this one.