According to ESRB, this game contains: Lyrics, Mild Violence, Suggestive Themes
With regards to the ESRB rating, I'm clueless as to where the Mild Violence and Suggestive Themes are in the game, but I assume they are hidden in one of the background videos along with the Lyrics that Parents are being advised to watch out for. Basically, this is MTV-level material, although it contains nothing as lurid as some of the music promos that station airs on its daytime playlist.
As for fans, if more Lumines is the craving, then Lumines II is the cure. Most will be happy that the mechanics remain untouched, but it does mean that the incentive for buying the sequel is ‘limited' to continuing the chase for high scores against new skins and to delving into the revised bonus modes, where thoughtfully extended structures make them more lasting foils to the main game than before. Overall, it is a comprehensive puzzle package, so fans and newcomers alike will find plenty to get their teeth into.
I feel I should note that the game is as visually busy and intense as they come on PSP, and gamers with visual sensitivity or epilepsy are advised caution when playing, as focusing on the screen for too long can be disorientating even for regular players. It is also worth bearing in mind that, given the rules of the game, any visual disability that affects color- or pattern-recognition skills may cause difficulty or confusion during play.
Deaf and Hard of Hearing gamers will miss out on the lavish audio feedback, and while none of it is actually necessary to play the game, it is where Lumines derives much of its unique appeal. Puzzle and Mission play modes owe much less to that audio experience, however, and Lumines II remains a well-crafted puzzle game regardless.