Bought this as a present for my other half and have since stolen it! The basic premise is that you have to perform 1 or 2 functions (done via the touch screen) in time to music. These functions are a basic tap and a flick, achieved by holding the stylus on the screen and flicking the wrist. At first glance it seems overly simplistic, but it most definitely isn't!
The music is accompanied by animations done in cute DS style on the top screen that range from ping pong to backing singers. The animations react to your taps and flicks in often unexpected ways. This extends to the menus, which are functional and fun. It's presentation is simple, colourful and goes well with the general feel of the game. The scenarios are sometimes so bizarre it's comical, such as the Easter Island singing heads!
The game really shines when it comes to the music. There are furious beats, saccharine pop songs and guitar riffs accompanying the animations. The sound is brilliant and really makes the experience gel together. I can highly recommend headphones as the fidelity of the music is exceptional, and is the highest quality of sound on any DS game.
The only thing that I can say against this game (although it's not enough to take a star away) is the punishing difficulty. All of the scenarios can be completed even if you make mistakes, but getting the perfect score requires practice and a decent understanding of rhythm. If you are prone to losing a rhythm then you may struggle on some the harder scenarios. Not a huge problem, but when getting a perfect score gives you a medal, with which you can buy mini-games and songs with, not being able to get a perfect score can be extremely frustrating.
To summarise, Rhythm Paradise is an immensely fun game with addictive gameplay, fun visuals and superb sound. If you like tapping along to a beat then this is for you, however if you are rhythmically challenged it can hamper progress at some stages in the game. But as they say "practice makes perfect". Buy it, you'll be pleasantly surprised.
I suppose I'll have to let my other half have a go now...