Personally, If i voted, I would vote for Obama. Like every president, he has his deficiencies, but he completed most of what he set out to do.
he [to a point] legalized abortion (I disagree with this move, but this was one of his stated goals, so...)
he re-vitalized the economy (Look at the stats: the recession is over the bad part)
he passed his stimulus plan (which could have been better if the republicans hadn't blocked him)
he would have created nationwide free health insurance if the republicans didn't block him
and as a bonus, he killed Osama bin Laden
If did not vote for him in 2008, then I believe it is completely your choice as whether to vote for him now, but if you did vote for him in 2008, then I recommend staying with him, as I don't believe the republican party has a better alternative, although I may be biased, as I consider myself to have left-leaning tendencies. If you wont vote for him just because he's black then SCREW YOU.