This has to be one of the most frustrating texts I have read in a long time! I've never read anything by Plantinga before, but my thoughts of him after reading this are not very high... Dennett is again and again clearly and carefully laying out the obvious facts of the matter without directly arguing against the existence of god, which would be besides the point in this debate, or rather, any strong arguments against god's existence would render the debate meaningless since religious beliefs means beliefs in the existence of god and belief in things the existence of which can be argued against rationally are certainly in conflict with science which, at a very minimum, requires the belief only in claims which can not be rationally falsified. But maybe this is at the very core of the debate? In any case, this is not the line of reasoning pursued here. Instead, Plantinga spends all of his time making rather silly claims about the supposed impossibility of unguided evolution generating minds capable of tracking truth, despite Dennett's insistent claims that this is exactly what brains do, tracking truth is what differentiates a "good" brain from a "bad" one (at least from the perspective of natural selection), there might be other adaptive properties of brains, but this is definitely one of the principal ones. Plantinga completely ignores this point until the very end of the book, in which he briefly mentions this argument (without really countering Dennett in his presentation of it) and immediately dismisses it for a ridiculous reason that seems to consist in the simple fact that not all parts of the brains of all species of animals host beliefs (which seemingly in Plantinga's mind are needed to host truth). His "argument" here is something along the lines of: "Frogs don't have beliefs about flies, they merely have indicators of flies which they act upon. The adaptability here concerns the reliability of the indicator". The obvious thing that Plantinga misses is that truth is essential here! The indicators of reliable if the proposition corresponding to the thing they are indicating is true, which means that the indicators indicate facts, rather than non-facts. We don't talk about beliefs until we come to humans who are capable of articulating their thoughts about subjects, but beliefs correspond to facts in the same way as indicators do, good, adaptive beliefs correspond to truths about the world, facts just as good, adaptive indicators correspond to facts. We have evolved to a high enough level that we can formulate beliefs about the world as opposed to just act upon our indicators, but the same basic fact about the adaptability of our brains' properties remain: they need to track truths if they are to be reliable, therefore, good truth tracking equals high adaptability. Plantinga does not seem to want to believe this and it seems clear from this part of the book and indeed most of the rest of his presentations that he prefers to start out with his pre-established beliefs about god (as being all-knowing, all-powerful, good, the source of our abilities whether those be truth tracking or ability to "know" god, whatever that means...) and to spend all the time remaining after enumerating his mantras in showing how god must have had a hand in it all.
Perhaps the most damning thing for Plantinga in this debate is that he insists on again and again presenting Behe as am authority or at the least a reasonable person (or at the very least a person that should be references by someone wishing to be taken seriously) without taking any consideration of the simple fact that Behe is someone who is universally rejected as a kook by the scientific community (Dennett refers us to a couple of devout Christians who agree with that assessment). When you refer to a person writing about a subject (in this case evolution) because his views "seem reasonable" to you (which is basically all Plantinga says about Behe), and hold your intuitive layman, religiously motivated opinion of him above that of the informed opinion of the community of scientific experts, you have crossed so far over the line that you should have to do a hell of lot of repair to your reputation before anyone ever considers your opinion on that particular subject every again. In fact, I'll go ever further: dismissing the universally accepted opinion on a scientific subject by the scientific community as a layman in that subject shows that you are incompetent in speaking about science at all, you simply have not understood its methodology!
There are many, many more points to comment upon but I'm tired and not a tiny bit pissed off at Plantinga's complete inability to understand Dennett's line of argumentation. This book has made my blood boil like few others... Do read it though, Dennett is brilliant and has the patience of a saint! (Figuratively speaking of course...)