Summary: The LEGO characters are cute and the music is good. However, I was disappointed with the interface. It is not what you would expect from Rockband. You only use the left, up , X and A controls to hit the notes as promted. Even though the DS has a microphone, it is only used in this game to activate the bonus powerup, and not for singing. I think this game would be better on the PS3 or Wii where you can use the real Rockband instruments.
Summary: I did enjoy this game a lot, but the main problem I have is the 'band groove' thing which means you have to continually switch instruments during songs. It makes it quite hard to get into the mood and feel like you're actually performing the songs.