I'm not usually a massive fan of rhythm and dance type games, but was strongly recommended to buy it. Needless to say, I'm very glad I did.
The basic story is that whenever someone cries for help to overcome a major problem, the Elite Beat Agents are there to help them overcome it, whether it's to help someone direct a successful film, or to more bizarre problems like helping someone overcome a fire breathing golem.
The concept is very simple. You just tap and slide the numbered circles while spinning a wheel from time to time to the music being played.
It's a very simple game to get into, as you'll eventually begin to time your taps well after only a few goes, and doesn't start off to hard to begin with. However, as you progress, you'll unlock more, harder songs to beat, and eventually unlock harder difficulty levels. When I mean harder difficulty's, I mean MUCH harder. I'm still stuck on the final song on 3 stars, and have heard there is AT LEAST one more harder setting. It's not a game you'll finish in a few days unless you're very quick. This could put some people off mind, but will give many people a good challenge.
It also boasts a good multiplayer, even through one cart. I've only done this via one cart, but this alone was good to play against someone, flowing smoothly without a hiccup on either side.
Lastly to mention is the lovely cutscenes and animation detail before and after each song and cutscenes during the song. All of them are in Japanese style anime (This game is based off the Japanese original after all), and all are worth watching at least once through just for it's weirdness. In fact, it's worthwhile going through each song and purposefully messing up (Having your bar in the 'No' bit). The cutscene is usually humerous to watch. The agents themselves look nice in their 3D models, and dance on the screen fluently with no slowdown at all
Overall, this is a great game that boasts great graphics, very good gameplay, and long lastability IF you challenge the harder difficulty's (Which I'm sure you will). A strong multiplayer to boot makes this a must have title on the DS.