If the consept of Rock Band is familiar to you then this brings nothing new, only the background animations are now played by Lego characters. To me, this is more funny than the "serious" characters in previous versions. Especially the Lego dudes based on real musicians such as Queen or Iggy Pop are hilarious. The song list is a great party pack, but this is of course a matter of opinion. if you like Rock Band then this is highly recommendable.
Oh yeah, you can also disable the pedal from the drums wich is great, bacause I hate that thing!