While this episode doesn't tread new territory, conceptually (Carpenter's brilliant "In the Mouth of Madness," for instance, or the much less brilliant but still charming "Stranger than Fiction," or that episode of "Masters of Horror" and so on) it does manage a couple of twists on the concept, with the final twist being just good enough to bump the episode up a point. Without revealing anything, that final twist did seem to have a plot hole, or, depending on how you look at it, a character error, but I'm willing to let that slide on account of the mental state of the person involved.
In a similar vein, some campy acting from secondary characters can be justified by the nature of the conceit here. I'm uncertain how much I buy the motives of the primary antagonist in the end, though. As with the first episode of this series, a time-crunch issue is fairly glaring, at least in this regard, because the character isn't sufficiently developed.
In any event, it's a pretty decent episode. Not an all-time classic of the genre, but interesting enough to be worth watching.