What were some positive and negative effects of the French Revolution?

The French Revolution had many positive effects. It eliminated the old class system under the Bourbon monarchy, one which gave preferential treatment under custom and law to clergy and to the nobility. The Revolution established religious tolerance for non-Catholics, and many of its legal reforms, which included trial by jury, habeas corpus, free press, and other civil liberties, were established (at least nominally) under Napoleon and continued into the nineteenth century. The French Revolution also inspired revolutionaries throughout Europe who sought, with varying degrees of success, to bring many of its liberal reforms to their own countries. 

However, these limited gains were won at a terrible price. The Revolution cost the lives of hundreds of thousands of French people, many of whom were totally innocent. We think of the extreme violence of the Terror when we think of the excesses of the Revolution, but the Revolution led to more than two decades of almost constant warfare which devastated Europe and brought a dictator/emperor to the French throne in the form of Napoleon. Many of its more liberal reforms, including women's rights and abolition of slavery, were rolled back under Napoleon. Europe would not see such turmoil until World War One, and it is difficult to say that such changes as did emerge from the Revolution were worth the human cost.