ADDED: Here's a big WaPo article on Bush's reliance on Petraeus's judgment:
In the waning months of his administration, Bush has hitched his fortunes to those of his bookish four-star general, bypassing several levels of the military chain of command to give Petraeus a privileged voice in White House deliberations over Iraq, according to current and former administration officials and retired officers. In so doing, Bush's working relationship with his field commander has taken on an intensity that is rare in the history of the nation's wartime presidents....Is that not what Obama is also offering to do when he said "I will always listen to the commanders on the ground"? Or is there some important order imposed by filtering communication through the military chain of command (as many quoted in the linked article are saying)? Is Bush exhibiting his particular management style, or has improved technology changed the way other Presidents will operate?
Bush's relationship with Petraeus marks a departure for modern war presidencies. Franklin D. Roosevelt, Harry S. Truman, Lyndon B. Johnson, George H.W. Bush and Bill Clinton left it largely to their military advisers in Washington to communicate with field commanders, according to scholars of civilian-military relations....
But during the George W. Bush administration, improved videoconferencing technology has allowed the president to communicate to an unprecedented degree with commanders on the battlefield and, his advisers say, immerse himself in the details of the war.