The previous post did an admirable job in articulating the strengths of the Enlightenment. If there was a potential disadvantage to it, I would suggest that it lie in its applications. The Enlightenment teachings, in particular the faith in scientific progress and rationality, helped to solidify the idea that all problems can be solved and that insecurity and doubt are elements to be overcome. I think that the application of this would be the Utopian societies rooted in a form of positivism that strove to root out human freedom, dismissing it nothing more as a part of an unbalanced equation. This same misapplication of rational thought can be seen in the theories of "Social Darwinism," and other forms of social and political orders that eliminate individual autonomy in the name of something supposedly larger. In no way would I fault the Enlightenment for this, but the type of rationalism that was endorsed through the Enlightenment was misapplied by those who came after it.
The Enlightenment laid the foundations for our modern world in that it moved us towards a society based more on ideas of reason and science than on religious faith. Before the Enlightenment, the Bible was seen as the definite authority about all questions. This meant that people were not all that interested in reasoning questions out for themselves.
With the Enlightenment, came an emphasis on proving things scientifically. People started to be more interested in finding out how the world worked; discovering physical laws by which the universe ran. This change allowed us to have the sort of technologically-based society we now have.
As far as whether this is positive or negative, you'd have to ultimately decide for yourself. I imagine the positives of all our scientific knowledge are fairly clear. In terms of negatives, you might argue that a loss of religious faith is a negative. Or you might argue that technology has had a harmful effect on human relationships.
Positives: We choose to seek scientific explanations and reasons more than the belief in a region.
Cons: Less desire for spiritual fulfillment.