I thought the same thing after the 11th. Not to be mean spirited but I thought those paddles in his chest were probably going off like a strobe light. Then I saw him the following Sunday morning on Meet the Press. He was clearly alive and not stroked out. His message and method of delivery made two things very clear to me. First, he was in charge of the country in the hours following the attack (example-he stated that he told the SS he was not leaving the area below the White House beacuse it was the only center for center for secure communications). second, he did not want to appear to be running the country, and wanted everyone to rally around W, not him.
I believe there is a distinct division of labor right now. Cheney is running things and doing what needs to be done "hands on" while W is dealing with the press, politicians, pulic, foriegn leaders, etc..