I once had the opportunity to share some beers for about half an hour with someone who had spent a significant amount of time with Cheney.  The person was famous, and the revelation of the name would damage him or her professionally.  The person, who was somewhat sympathetic to the Administration was very clear about their opinion of Cheney.   "He's a maniac," I was told.  Its no suprise then, to read Newsweeks lengthy dissection of the VP:

Has Cheney changed? Has he been transformed, warped, perhaps corrupted—by stress, wealth, aging, illness, the real terrors of the world or possibly some inner goblins? The few who know him (and few really do) aren't saying much, except to argue that he takes a longer view than the mean politics of the moment. But there is no doubt that Cheney has become less amiable, less open, less willing to conciliate and seek common ground than he was as a younger politician. A man who was shepherded by the Secret Service to his bunker during 9/11 has stayed there—even when that has not been helpful to the president.

Even more frightening is Cheney's willingness to lie:

Cheney testified to the 9/11 Commission that he spoke with President Bush before giving an order to shoot down a hijacked civilian airliner that appeared headed toward Washington. (The plane was United Flight 93, which crashed in a Pennsylvania field after a brave revolt by the passengers.) But a source close to the commission, who declined to be identified revealing sensitive information, says that none of the staffers who worked on this aspect of the investigation believed Cheney's version of events.

A draft of the report conveyed their skepticism. But when top White House officials, including chief of staff Andy Card and the then White House counsel Alberto Gonzales, reviewed the draft, they became extremely agitated. After a prolonged battle, the report was toned down. The factual narrative, closely read, offers no evidence that Cheney sought initial authorization from the president. The point is not a small one. Legally, Cheney was required to get permission from his commander in chief, who was traveling (but reachable) at the time. If the public ever found out that Cheney gave the order on his own, it would have strongly fed the view that he was the real power behind the throne.

  One heartbeat away.