I'll give him a C-B with leaning towards B. He inherited a pretty dismal situation but I would consider any remedy to the current economic troubles does not rest solely on his head. There needs to be a lot of work done by the legislative and administrative branches in addition to efforts by states, municipalities and other countries globally. Mainly what I am disappointed about is his inability to adequately lead Congress. Congress shares most of the blame but I feel that he needs to be more successful in trying to get needed legislative duties through, the nadir being the failure of the budget committee last fall.
On the other hand, I feel he has done very well with the more direct responsibilities of the office. His foreign policy has been very successful. He has more or less kept to the timetables of pulling out of the current wars, has made more efforts in diplomacy, made China a stronger focus for future policies (and the progress in Burma has been excellent in this regard), has done very well with taking the risks for special operations (pirates, OBL), his handling of Libya so far has seemed to have gone well and has kept a strong stance in other areas where I was afreaid he would have instead acted too conciliatory (drone usage).
I'm more interested in trying to get a dramatic change in the legislature this upcoming election as opposed to the administrative.