I’ve been thinking about this original question a bit lately, as one of the ID stars, Stephen Meyer, has a new book coming out at the end of March.
As several have mentioned in this thread, there is a range of views among IDers, from young earth to accepting common ancestry. And most of us evolutionary creationists think God is intelligent and in some sense designed things. So the difference between us and IDers is less about the conclusions than about how you get to those conclusions.
Meyer’s new book is The Return of the God Hypothesis. And it appears to be straightforward natural theology: scientific premises are used to generate a theological conclusion. In his case: the universe had a beginning, fine-tuning of physical constants, and information in DNA ought to lead us to believe that there is a personal creator God.
So, I agree with his conclusion. What concerns me about the argument to get to that conclusion is two-fold: 1) Typically (I’m not commenting on Meyer’s book here, since I haven’t seen it), ID adopts some alternate version of science from what has emerged through the consensus. They vociferously reject charges of “god of the gaps”, but there is usually just a semantic difference with what they’re positively claiming: the scientific explanations aren’t able to completely explain some phenomenon, and so an intelligent designer is invoked as the “hypothesis” that does completely explain that phenomenon. My first concern is that people who already accept the conclusion are now given more fuel to distrust the consensus science. That might result in some short-term gains in bolstering the faith of such people, and even in attracting some others to that conclusion (I know a couple people who became theists because of such arguments), but I fear it is not a productive strategy for the long-term. Science has a way of figuring things out and advancing such that what was previously thought inexplicable does ultimately have a natural explanation.
Concern #2 is that people who don’t accept the conclusion to begin with are driven further away from considering it because of the non-standard science employed. They react with: you want me to believe in God and this is the best argument you have? Never mind.
Of course IDers have responses to these, but I think it points to the essence of the disagreement between most IDers and most ECs. Instead of that kind of natural theology, we tend to favor what Alister McGrath has called a theology of nature. That takes the theological conclusions and works them into an interpretation of nature – rather than taking scientific premises and arguing for theological conclusions. Our approach interprets science in the light of theology. But it accepts the consensus findings of science.