Personally, I would give him an A-. He has inspired hope, confidence in USA and in the world. He has made a start towards fixing the economic meltdown caused by Bush and the Republicans. While it is too early to say that we are out of the woods, there are tentative, tantalizing glimmers of hope.
In terms of foreign policy, when he was tested in Somalia, he passed the test with flying colors. In social policy, he reversed the much despised Mexico policy and legalized the embryonic stem cell research. So there is plenty of good news to cheer about.
On the minus side, the economy is still in the tank. We can see a faint light at the end of the tunnel, but we don’t know if that really is the end of the tunnel or it is just a train headed in our direction.
In foreign policy, Iraq and Afghanistan still remain a challenge. Also Obama gets a poor grade for his nominees. Many of them are capable, expert diplomats in their own fields. However, many of them have been racked with tax problems. Obama could certainly use a better vetting process.
Anyway, overall Obama has put the country (and the world) on the right track. So he gets an A-.