Now, I have read it, so here are some thoughts.
I'll begin by accentuating the positive. It is impossible for anyone who watches the philosophical scene and who has an independent turn of mind not to like Plantinga's spunky injunctions to (Christian) philosophers to get some spine and stop trying to fit themselves and their philosophical ideas into the Procrustean bed of whatever happens to be the fashion du jour when they go to graduate school. To that I say "Amen" many times over.
Plantinga is especially amusing when he tells the cautionary tale of logical positivism and the verificationist criterion of meaning:
On these grounds [of the verifiability criterion] not only theism and theology, but most of traditional metaphysics and philosophy and much else besides was declared nonsense, without any literal sense at all. Some positivists conceded that metaphysics and theology, though strictly meaningless, might still have a certain limited value. Carnap, for example, thought they might be a kind of music. It isn't known whether he expected theology and metaphysics to supplant Bach and Mozart, or even Wagner; I myself, however, think they could nicely supersede rock. Hegel could take the place of The Talking Heads; Immanuel Kant could replace The Beach Boys; and instead of The Grateful Dead we could have, say, Arthur Schopenhauer.
Plantinga's other examples are good, too. He warns against assuming the truth (or even the plausibility) of naturalism, anti-realism, or determinism and then wringing one's hands over the fact that Christian doctrine is incompatible with these trends of thought. He also rightly dismisses convoluted attempts to reinterpret the obvious meaning of traditional Christian teaching to make it compatible with trendy views. One of his examples here is the suggestion that "God exists" be reinterpreted as, "Some men and women have had, and all may have, experiences called 'meeting God,'" to make it meaningful according to verificationism. No doubt we can all think of more contemporary examples. ("Christian physicalism," anyone?)
Plantinga is also quite right that if you have justified belief in the existence of God, this will rightly have evidential relevance to other things you believe. You will then have already in hand a reason to reject physicalism, anti-realism, determinism, and so forth. (The big difference between me and Plantinga, though, does lie in our notions of justification.) And there is nothing wrong with using the justified beliefs you already have in doing your philosophy. Here he is especially good on integrity, or what he calls by the rather clumsy word "integrality." It is obviously folly for a Christian philosopher to throw himself wholeheartedly into defending a set of philosophical views manifestly at odds with his Christianity without asking himself some questions about consistency. In particular, he should ask himself why he has adopted these views and whether doing so was the result of clear thinking, very strong arguments, and the search for truth or rather was a chameleon-like adaptation to his philosophical environment. And if the latter, he should stop, turn around, and go back.
The most important insight that I think any philosopher (Christian or otherwise) can gain from Plantinga's injunctions is the realization that what is presently popular and even dogma in an intellectual field can be and surprisingly often is completely wrong. (Now if only Plantinga would have the confidence to apply that insight to New Testament studies...But I digress.) If something sounds like gibberish or sophistical claptrap, don't be so diffident as to assume that the problem must lie with you. Maybe it is gibberish or sophistical claptrap, and that screaming sound you hear is your common sense rebelling. Students, in particular, are unfortunately susceptible to Emperor's New Clothes Syndrome, partly out of fear of bad grades or of tanking their careers, partly out of genuine self-distrust. No doubt more of them need to learn to be like the little boy in the story.
This is all good.
Where I think the article needs some correction is in its very strong emphasis on all of this as a specifically Christian endeavor and a specifically Christian issue. After all, doesn't Plantinga think that non-Christian and even non-theist young philosophers are capable of seeing serious problems with naturalism, et. al.? It seems that he must, considering that he himself has his own well-known "evolutionary argument against naturalism." As an internalist, I'm not even sure that that argument works, but the point is that Plantinga obviously thinks it works, and it's not something you need to be a Christian or even a theist to go along with.
Readers of my earlier exchange with Bobcat on the notion of "Christian philosophy" will know that I am not positive to that concept and may be surprised at all the positive things I've said so far about Plantinga's article. His article is first and foremost an injunction to develop something very much like "Christian philosophy." He even goes so far as to say that Christian philosophers are the philosophers for the Christian community and should take their whole set of projects from the Christian community.
And all of that really is the sticking point for me. I think philosophers should strive to be good philosophers, to get it right. And I think the positions Plantinga discusses as examples are philosophically wrong-headed. Rather than saying, "I'm a Christian philosopher, and I work for the Christian community. I assume a Christian perspective as a starting point, and that's why I'm not a physicalist," would it not be at least as good, better, in fact, for a philosopher simply to do excellent work in metaphysics and the philosophy of mind arguing for dualism, arguing against physicalism, and so forth? Would it not be better for him just to be a darned good philosopher and to work out in detail and publish about the philosophical problems with various untenable but popular positions?
If Alvin Plantinga himself were asked, in a philosophical context, by a non-Christian, what is wrong with naturalism, would he say, "Well, I'm a Christian, so of course I reject naturalism"? I doubt it. I assume he would bring out his EAAN. I'm an evidentialist, and Plantinga and I are very far apart on epistemology, so I don't even "start from" Christianity or the existence of God in the same sense that Plantinga does. That is, I don't treat "God exists" as "properly basic." But let's put the same question in terms of my positions: Suppose someone asked me in a philosophical context what is wrong with naturalism. I would not start talking about the resurrection of Jesus Christ. I'd probably go straight for something more like a Lewisian self-refutation argument or for a Cartesian argument for the mind. That is to say, both Plantinga and I presumably believe that one can argue against the positions he cites qua philosopher even without doing so qua theist philosopher. Yes, it's true that if you are a theist, and if you are so rationally (bearing in mind that Plantinga and I have different notions of "rationally" here), you have that additional reason to reject social constructivism, physicalism, naturalism, and many another undeservedly popular -ism. But why start at that end? It isn't necessary to do so.
It should be possible to predict from the fact that a philosopher is a Christian the positions he is likely to take on other issues. There is nothing wrong with this, nor does that correlation and predictability reflect some sort of failure on the part of the philosopher to follow the argument, care about the truth, and so forth. On the contrary. Since Averroism is false, there are not "two truths." There is not one set of philosophical truths which is contradictory to the truths of revelation. Given that Christianity is true, true philosophical positions will of course be consistent with Christianity. A philosopher who calls himself a Christian but has tied himself into a pretzel to modify traditional Christianity and make it appear friendly to something presently popular is probably in need of a spine transplant, if it's not already too late.
But it doesn't follow from this that the only or the best route to take as a Christian philosopher is to "start from God" in making all philosophical arguments and to regard one's philosophy as always distinctively "Christian," as though one's positions cannot be defended and trendy nonsense rejected on purely philosophical grounds.
There is much to like in Plantinga's article, and I encourage not only Christian philosophers but all philosophers to read it. I'd love to see more bluff-calling even on the part of non-Christian philosophers with common sense. But it does not make me any more friendly to the establishment of a field of "Christian philosophy."
P.S. I think it would be interesting for my philosophically knowledgeable readers to list philosophers they know of (far more than I am likely to have heard of), especially living philosophers, who are not theists at all but, say, reject naturalism, take an agent-causation view of free will, etc.