Hearing McMullin speak about the history of the development of early modern philosophy in tandem with modern science was one of the delights of my first year in grad school. I appreciated that it was a good story, well-told. Thinking about science and philosophy as sharing metaphysical commitments which were particular to the Church and to origins in Hellenistic philosophy implicitly presented the thesis that if Church history had been different, the questions and tools available to 17th century science would also have been different. This was consistent with my learning to take a historical and sociological approach to the development of scientific methods and institutions (but in a way that respects, rather than undermines, the intuition that science and philosophy are progressive). That lecture probably reinforced the track I was already starting to follow. In hindsight, much about the talk was probably already obvious to many in the audience, and I know of others who have given more detailed accounts of how scholastic metaphysics affected the development of modern science (Dan Garber, especially), but at the time I was happy to be able to absorb these historical points and to hear them in the form of a fascinating narrative.
I've also found his talk on "Values in Science" to be provocative at several points and useful for several projects. I just learned from Michael Ruse's piece that it was the PSA presidential address that year--I don't believe it's marked in that way in the printed collection.