Except that would only give her 2 years of gubernatorial experience before running. It just wouldn't be viable, and she can't wait until '12 because another Dem could most likely take the WH in '08.
Even 2 years of executive experience on her resume would be helpful. Every President elected in the last century has been a former Governor. She would be well positioned to take advantage of the prominence that goes with the role to make her imprint on New York State and then run for President. The party would certainly get behind a successful Big State Governor.