Recently, the concept of irreducible complexity coined by Michael Behe has become cause celebre for the creationist movement. There are several problems with Behe's proposal vis-a-vis creationism. First and foremost of which all of his examples are actually quite reducible. His model argument is the mousetrap which consists of 5 parts; spring, trigger, baitholder, jaw and base. None of which can be removed or the trap will not function according to Behe. With a little creativity a mousetrap can be made from the spring alone. Similarly Behe erroneously attibutes this property on other things.
Furthermore, many of the proponents of this argument from design are theologians and philosophers and few biologists reject evolution on this basis. There is also plenty of literature that undermines Behe's theory. Hume effectively refuted the argument from design over 200 years ago. Richard Dawkins renders Behe's assertion moot in a book called The Blind Watchmaker.
With respect to basic logic Behe uses a false dichotomy. Behe only considers two possibilities contigent upon the existence of irreducible complexity, namely evolution or creator.
Creationist who dismiss evolution also dismiss a preponderance of evidence such as analagous proteins and biochemical pathways that exist across phyla, not to mention established concepts like allopatry or fossil records.
Creationists have taken irreducible complexity up as a concept that further's their cause. What they fail to realize is that Behe himself does not deny evolution he allows for the assumption of the existence of an intelligent designer based on the existence of his theory. A theory that includes a property which has yet to be accurately attibuted to anything. This is not to say that a creator does not exist, merely that the concept of irreducible complexity is no basis for that assertion.