For the most part, Rhythm Heaven is stylus controlled, though the shoulder buttons are used briefly. While holding your DS or DSi sideways, you alternately slide the stylus across the screen, make a flicking motion, tap it for various minigames, and hold it against the screen at varying times. The controls are fairly easy to pick up, but the different game levels themselves are another matter.
I'm not particularly musically inclined, so I'm not sure if that makes much of a difference, but I found Rhythm Heaven to be quite difficult. It was often a real struggle for me to just squeak through each level with an "OK" rating on a level. Considering that you must score high enough on one game to unlock the next, I often found myself getting frustrated. It can be cute and fun at times, but the reality of Rhythm Heaven is a far cry from the relaxation and giggles pitched to the unwitting gamer in the Beyonce commercial--or such was the case in my experience, at least.