You know, I don't believe I've ever seen anyone attempt this pairing before. You've created a touching story of a fleeting love affair set outside time, exactly the sort of thing that would take place during a war - a relationship that would never happen under ordinary circumstances but that provides an accidental escape for both parties from constant threat and despair.
The attack on Minerva is horrifying - I hated to imagine her being tortured senseless. But her recovery and the warm, forthright, intelligent personality revealed behind the professor of high standards and high collars piqued my curiosity. I could easily believe in this less careworn, more open version of Minerva, someone who doesn't remember living through multiple wars. Meanwhile Neville's self-deprecating but steady assumption of a strength and courage he doesn't believe he has unfolds plausibly; there's no sudden steeling of nerve, no unearned heroics. It all occurs in small increments of choice, a perfect example of Dumbledore's philosophy. His shy, desperate (and slightly Freudian) longing to lose his virginity to his formerly intimidating head of house (however ethically dubious it is to accept her offer, knowing in her right mind she would never consent) rings true. The wish-fulfillment romance under the shadow of death is a rite of passage, something that can't last because it depends on an unsustainable absence (Minerva's memory). For Neville, desired with adult passion by someone he respects, it's a bridge to adult responsibility. For Minerva, it's something gained and lost in her restoration to her complete self.
I love the spirit of cooperation and conspiracy among the teachers and the interrogation scene in which Snape searches Neville's mind, especially the hallucinatory image of the slimy mass Snape probes with his fingers. I also like the way Neville almost welcomes the sight of Snape's sneer because it's familiar and human, unlike the headmaster's current icy mask, yet another sign that Neville's perspective is maturing under the pressure of necessity. There are many nice moments throughout (the Minerva/Goddess banter, for instance) that pay tribute to Neville's sweetness and stubbornness. And for me, the ending is wistful rather than heartbreaking because no one is hurt. Minerva the Fierce is back and won't be haunted by memories of a transgression she would forever hold against herself, while Neville has memories to treasure and a new understanding of the fact that his professors aren't merely authority figures but real people.