One of the most fast-paced, highly-addictive games ever that any action-puzzle fan must absolutely try.
The only areas that drag down the quality of N+ are the graphics and the level of frustration the game can induce depending on the level. The graphics are extremely simple by today's standards, but they do not significantly degrade the gameplay or the overall quality of the game. In other words, if the graphics are the the deciding factor in whether you intend to purchase this game, then the game probably isn't for you anyways. Otherwise, the action in the game is some of the fastest I have ever encountered and most of the time can only be described as "frantic," especially when you reach higher levels. The only other issue I have with this game is the level of frustration it can bring to the player. There have been a few times when I have wanted to throw my PSP through the wall or throw my X360 controller through the TV because of my inability to complete a level (after dying 100+ times on that particular level). However, those frustrations are completely obliterated and the level of satisfaction that much greater upon completing those frustrating levels.
Overall, I give this game an 8.0. The graphics are nothing great and the game can get very frustrating, but the super-fast pace and totally addictive combination of frantic action and puzzle make this game one that I recommend to anyone who enjoys action games.