Saw this the other day...
I'm not familiar with the manga at all, but the concept seemed interesting and the TV spots in turns creepy and intriguing. It was also being promoted like it was the second coming, so I went to see it with high expectations.
I was disappointed: I was really fighting to stay awake near the end. It wasn't a terrible movie, but it felt like it always just barely missed the mark. With one more pass at the script and a more inspired director, it could have been every bit as cool as advertised.
Even as people were dying bloody deaths and the airport blew up, I never felt any sense of urgency or danger for the characters at all. The only moment I felt at all on the edge of my seat was the creepy sequence where the cultists turned on one of their own in Kenji's convenience store, which was very well-done.
The other problem was how I never felt any of the characters in the huge cast really got to shine or show much personality. The characters never seemed to really grow past their typical manga stereotype roles, and it seemed such a waste of the much-hyped all-star cast. The only character I really enjoyed watching was Occho, whose actor managed to bring an unbelievable presence and sense of overall badassery to the role. But as he doesn't show until the second half of the movie, it felt like too little, too late.
My interest was piqued by the Tomodachi mystery, and I still thought the storyline was intriguing at its core. But I left thinking I'd rather start reading the manga to see its resolution, rather than watch the rest of the movie trilogy as it comes out.