"Presence" is currently up for a Hugo Award, and since I haven't yet read any of the other novelette nominees, I can't say whether it deserves to win or not, but it certainly deserves its nomination.
This is a carefull-crafted, well-modulated story which looks at a possible future near-cure for Alzheimer's Disease. Since my own grandfather had Alzheimer's, I can say with some authority that McHugh's presentation of the disease's effect on its victims, and on their caregivers, is sadly accurate. The prose in the story is clear, though not particularly stylish, and the story mostly avoids the kind of cheap sentimentality that stories about sufferers of diseases can often fall into. The ending is particularly well done, with no simple "cure", no easy solution, no sudden fix -- instead, McHugh offers a mutedly emotional ending, one which mixes hope with sadness and regret, the general pain of being human.
I have some reservations about the story, though not reservations about whether it should have been published or whether it deserves to be nominated for awards. As I said, it is an effective story, in some ways a beautiful story, and one which deserves to be read.
Taking all that into account, though, it seems to me to suffer from the same problems as Alice Elliot Dark's story "In the Gloaming", which John Updike included in The Best American Short Stories of the Century. I seem to be the only person in the universe who found "In the Gloaming" a frustrating story, one of those tales which gets labelled "poignant" and "sensitive" and "moving", but which ultimately manipulates the reader by offering no option but to feel for the characters and their plight. I think McHugh's "Presence" is a better story, actually, than Dark's, because there is some distance, and a difficult moral question is posed to the reader (we are left to wonder whether the main character's decision to subject her husband to the Alzheimer's treatment against his will was justifiable). For me, "In the Gloaming" was a sort of "disease-chic" tale, the kind of thing which gets made into softly-lit movies (it has been) that make audiences cry. Again, McHugh doesn't quite sink this low, but she also doesn't rise above some of the facility which disease stories offer to authors.
If we compare "Presence" to a classic by Anton Chekhov, "A Doctor's Visit", we can see some of what might have made McHugh's story into a truly remarkable work: a greater willingness to allow ambiguity in what is said between characters, less of a desire to portray every action with clarity for the reader, and more attention to the physical details of daily life in the world she created. I do think there are moments in the story where she nearly achieves this, and the relationship of the son to the rest of the family is a particularly strong choice which adds depth to the narrative and the characters, but there is not enough connection between the characters and the physical world they inhabit for the reader to be allowed the real resonance which great literature provides. Chekhov's story is half the length of McHugh's, and yet its world is more vivid (and in some ways more alien to us), its characters more fascinating because they are mysterious and hint at complexities beyond the frame of the tale itself.
I suppose it seems a bit silly to criticize a story which I've said is better than one included in a book called "The Best American Short Stories of the Century", but I often find myself wanting to criticize really good stories more than bad ones, because the really good ones come so close to greatness. There are a plethora of bad stories out there, hundreds and hundreds for every one story which is even mediocre, and thousands and thousands for every one story of "Presence"'s quality.
I can't help dreaming, though, can I?
(Note: I read "Presence" in Dozois's Year's Best Science Fiction: Twentieth Annual Collection.