Proponents of Darwinian evolution are antagonistic to ID, stressing the role of random chance within the process of "natural selection," and asserting that nothing more is needed to explain nature and life.
Evidence in favor of ID includes the exceptional fine-tuning of certain physical constants of the universe, as well as certain biological phenomena (such as the human eye or the body's blood clotting mechanisms) that seem to be "irreducibly complex." ID proponents maintain that this complexity is sufficiently great that a pathway of mutations and natural selection couldn't get you from point A to point B.
Some creationists have latched onto ID and diverted it in their direction, thus introducing more controversy than is warranted by the fairly modest claims of the original "Intelligent Design" theorists.
Pros and Cons
Pro: Intelligent Design gives a coherent explanation that hangs together.
Con: Intelligent Design steps outside the boundaries of science.
Pro: Intelligent Design explains what evolution must leave untouched.
Con: Intelligent Design only shifts the "unknown" another step backward by attributing its explanation to God.