The doctor says it's the worst case of pizza infatuation he's ever seen.
Because the DSi has no Game Boy Advance capabilities, this game compensates for that by making you use your stylus to execute notes. This seems innovative and maybe entertaining at first, but after you get done with the first area, which only sports two songs, you'll begin to wonder why you didn't spend your points on something better.
This game also allows you to play on the drums, which is a tad better than playing on the guitar, but has the same problem of becoming boring after the first two songs. You have to use the L Button to use the left drum, and A, X, Y, B, G, Q, and R to use the right drum (it seems a bit awkward to have a plethora of buttons to use for one drum and only one for the other; I just use L and R simultaniously)
You're also limited to four wanna-be rock stars, and that's it. No extra unlockable characters, no prizes for completing things with complete accuracy, just badges. Badges are completely useless as well. You get them by completing random things. In fact, you get a badge for getting a badge which is obtainable right at the beginning of career mode. Joy.
Oh, and there are a lot of cheesy pizza jokes (no pun intended). Seriously.
Please, save your 500 points and get something sensible.