Wilson claimed from the beginning that Cheney sent him to Niger--that never made sense. This proves that his wife was responsible.
That was already known.
The significance is that Wilson claimed that the Whitehouse had manipulated the intelligence report as an excuse to war.
Cheney said that he never saw Wilson's intelligence report, which is probably true because the CIA says that there was no written report. This doesn't exactly ring true with anyone because the CIA always has written reports. It may be that Wilson didn't write a report, but someone else, possibly Plame, did and they are playihng games with investigators.
My guess on this whole case was that, perhaps the administration knew that Wilson was lying about everything, but the documents involved were too sensitive to release and needed to discredit Wilson, rather than discredit the lies, because they had no proof to show the people
The big question is, why did Wilson lie about the whole thing? Was Wilson working for anti-US interests inside our own government, or just anti-Bush interests? We know that he had worked as a national security advisor for Al Gore in the 2000 election.