I think Coyne is right both about humans not being inevitable and about the importance of this question to religious folks. If Stephen Jay Gould was right about humans being unlikely to evolve a second time were we to replay the evolutionary process, then Christianity is really in some very serious trouble. It's pretty hard to argue that humans are the point of creation if it's a serious possibility that evolution would never have gotten past the trilobite.
No doubt it would be hard to argue, at least granted certain presuppositions; but humans aren't the 'point of creation'. And this has in fact been a pretty common position in the history of Christian theology, whatever its status among the sorts of people Rosenhouse reads; and, indeed, the same goes for lots of 'religious folks' outside of Christianity. We have no particular reason to hold that we are cosmically significant by nature; God is cosmically significant, to be sure, and thus friends of God, to use the old phrase, have a sort of indirect significance. But in a sense the whole point of human life is recognizing that we are not the point of the world. Of course, we are still pretty significant to ourselves, and we can do some pretty splendid things like seek God and write poetry and figure out the gravitational constant, and we can do some thoroughly horrible things like rape and genocide and torture; but that's a different sort of significance.
And as to inevitability: any 'yes' or 'no' answer on that point would have to be massively qualified on any position, because inevitability is always relative to a particular causal background. If you specify the causes sufficiently precisely, anything is inevitable, because you've narrowed down the causal options to the one effect; and if you are sufficiently general in your identification of the causes, nothing is, because you've broadened all the causal options to more than one effect. So if we ask whether human beings were inevitable, we have to ask, in light of which set of causes? Those constituting the entire evolutionary history right through to modern homo sapiens? Those involved in the formation of the earth? Those involved in the formation of the sun? The eternal plans of God? The cosmic radiation leading to this or that mutation? The early reproduction of the first eukaryotes? The diverging of the Diapsidae from the Synapsidae? Pick your set of causes, the details of your answer will depend very crucially on the causes you've picked. The causes set the possibilities.
UPDATE: In the comments Jason notes that in context he meant something much more specific than his words seemed to imply; taken in that more specific sense, I'm still not convinced, but I think it's a much stronger argument.