Another fine early-week offering. Clues like the somewhat silly 14A: Giver of a hoot (OWL), and 23A: Cuckoo in the head (SCREWY), seem slightly irreverent, which I count as a good thing. And were you surprised, as I was, by the lack of any "abbreviation signal" in 44A: News items often written years in advance (OBITS). I would have expected "... yrs. in advance," or something like that, or has "obit" become its own word now? I was similarly jarred by the answer ANTINUKE (11D: Like a "Better active today than radioactive tomorrow" sentiment). I guess it's not really an abbreviation, and I had no problem accepting it as a perfectly fine answer, I just wasn't expecting it, that's all. And, that's another good thing. It's as though Ms. Gamache were saying IREFUSE (12D: "You can't make me!") to conform to your puzzle-y preconceptions!
The theme was fine. Its kind has been seen before, but again, the revealer WISECRACK (60A: Witticism ... or, literally, a description of the answer to each of the four starred clues?) just seemed a little, oh - I don't know... , surprising. WILDGEESE (17A: *Migratory flock) seems a little odd, in relation to "Canada geese" or just "geese," but it's not out of the question, I suppose, to say "wild geese." We had "flying horse" at first for WINGEDHORSE (36A: *Pegasus, notably), but there I think the given answer is the better option. And, oh, how I miss Amy WINEHOUSE (30A: *Singer Amy with six Grammys). Before she died I had concocted an elaborate scheme in which she would, in maybe ten or fifteen years, have removed herself from the crazy music scene, taken some time off, and then eventually have a comeback tour wherein she would play small coffee-house type venues. I would see her then, with her wrecked, but still powerful voice, and a more (not totally) sober, yet still original and vibrant interpretation of all she chose to sing, which, in my imagination, would be all my favorite songs. It was a beautiful dream, wasn't it? Alas.