To my understanding, archaeological importance is about what we can learn from the discovery. So first a disclaimer; I do not know how much man has learned from recovering the Monitor, and nobody knows at of this moment what we will learn from investigating this ship (finding it in itself is not that big a deal).
The Monitor (and the Virginia (ex Merrimack)) changed the way wars was fought at sea. Thus it is one of the most important historical objects of naval warfare. (although it had severe and crippling limitations)
And although I recognize Arctic expeditions as much as the next Norwegian (a friend of mine is of Amundsen descent); in those days ships sometimes perished without trace. Amundsen himself perished, and has not been found.
I'm not saying this discovery is unimportant, but not _that_ important.
(Anyway I agree with parent, dead sea scrolls beats this discovery hands down (and maybe Tutankhamen's tomb itself)