While this game makes no improvement on the puzzle gameplay of 999, and the story is overall pretty unsatisfying, I'll give it some credit for taking the high concept of 999 and making it a core element of the game.
The most frustrating thing for me is that the end of the game didn't really feel like a proper ending. I'll play Zero Time Dilemma soon, but even if that ties up all the loose ends, it doesn't really reduce the disappointment of this game's ending.