All POD reviewers face a fundamental question. Do I post negative reviews of books that I didn't like, thereby potentially reinforcing the (frequently accurate) stereotype that all POD authors are, to be blunt, unskilled? Or is it better to try to elevate perception of the medium by focusing solely on works that I can wholeheartedly recommend? There plainly is not a "right" answer to this question, and the POD websites I've seen run the spectrum of review philosophies.
I follow a "does it deserve to be taken seriously" approach. That is, I am not limiting myself to wholly positive reviews, or even to works that I can recommend at all. Rather, I will review a POD book if I feel, in my sole and unscientific discretion, that the writing is at such a level that the book deserves to be taken seriously as a work of art. This obviously is a wholly subjective question. But that, of course, is almost the definition of the reviewing game.
Thus, the question of whether I ultimately agree with all of an author's choices, or enjoy his or her style, plainly will impact the substance of a review. However, so long as I feel that I can treat the author with respect, and a book appeals to me enough that I feel I have something worthwhile to say, I'll review it. To use a very non-POD example, I personally can't stand James Joyce's writing. But even I, begrudgingly, will acknowledge that he had, maybe, a little bit of talent. So I would review A Portrait of the Artist as a Young Man.
But that doesn't mean I'd have to like it.