... this just seems silly to me. So we (presumably) have some dust particles from this rock that (supposedly) has not been changed since the inception of this solar system. The evidence for it's stagnant status for the last "four-and-a-half thousand billion years" is "because the comet is made of ice". Have we not seen evidence here on earth that things may be frozen yet change?
Furthermore, all we have is some flecks of dust... belly button lint could tell us more about where we came from. And, even assuming that this is very informative dust, have we not already gotten data sent back from Mars?

I would like to think that all this dust is going to be useful for mankind, so please, someone, if you have a good reason for us going and collecting some flecks of star dust, let me know. Otherwise I will wait in hopes that NASA and their friends can prove me wrong while I sit here and contemplate the intricate properties of naval lint.