Successes: no terrorist attacks on the United States since 9/11; trusted Petraeus and made the courageous decision to start the surge; his commitment to fighting AIDS in Africa
Failures: did not make tax cuts permanent; overall budget mismanagement, failed to control spending, rarely used his veto; failed to reform social security and immigration
TBD: the decision to go to war in Iraq; to a lesser extent, the decision to go to war in Afghanistan; the Katrina fiasco; his role in addressing the financial crisis
This is my basic assessment of his presidency:
1. He trusted his instincts without agonizing over any doubts or alternative courses of action;
2. He was loyal to a fault, and he probably verged on cronyism;
3. He was well-meaning and sincere;
4. He was not an intellectual, but he was highly intelligent;
5. He deferred too much to Cheney, and thus looked weak at times;
6. He failed to control the rivalry between Powell's State Department and Rumsfeld's Pentagon, which is a big deal during a time of war; and
7. He was a consequential president, much like Truman, and his major foreign policy and national security decisions will be debated by historians for decades.
In other words, Bush had his successes and his failures. But the defining issue of his presidency--terrorism and Iraq--is the key to his legacy. Because of the importance of hsi defining issue, he may be remembered as a great president, or a horrible president. There really is no middle ground.