What were some positive and negative outcomes of the French Revolution?
I think the negative outcomes were mainly short-term and the positive ones long term.
There is no question that the French Revolution was needed. The Ancien Régime was brutal, denying basic human rights to the vast majority of subjects. There was no freedom of speech or religion and the nobility could act with impunity with no repercussions for such acts as raping female peasants or assaulting or abusing members of the lower classes. The Roman Catholic Church had also been corrupted by its alliance with the throne, with important posts reserved for members of the nobility rather than people with the best qualifications, such as piety or theological knowledge. As Brettd pointed out, much of the tax revenue, often taken from the poor and middle classes, was squandered on luxuries for the court rather than the common good. Creating a fairer and more democratic society was a strong and obvious positive.
The actual way in which the Revolution was conducted, though, was harsh and brutal. The Reign of Terror (5 September 1793 – 28 July 1794) was particularly brutal. Just as it is wrong to mistreat someone because they do not come from an aristocratic lineage, it is equally immoral to mistreat people because they do come from an aristocratic background. The ideal of liberty could not be realized until all people began to be dealt with equally as individuals, not as members of classes. The eventual outcome, though, of the current free democratic society is a strong positive.
On the positive side, one can easily argue that the removal of King Louis XVI was a step in the right direction, as he had bankrupted France, and his royal court lived with every luxury while people were starving. There were other injustices under the King and he became more and more like a dictator towards the end of his rule, as he tried to maintain his grip on power.
On the other hand, it's not as though what replaced the monarchy was any better, and in many ways, it was a lot worse. For the next 13 years France spun into a cycle of violence, revolution and counter-revolution, only to end in the disastrous reign of Napoleon Bonaparte, who led the country to war and defeat.