There's a lot to like here, and some that I personally did not love. Of course, by now you all probably know what my first complaint is: the hypersegmentation of the grid. Yes, the NW and SE corners are essentially completely isolated from the NE to SW diagonal section. Furthermore, all of the entries into those corners are via question mark clues or the misdirection clue for the 15-letter down answer, which adds to the difficulty.
Not that that should be a very strong mark against a Saturday, of course. It's supposed to be hard, and it definitely played that way. On my first run through the puzzle, I had multiple little bits of things here and there. I put UDON in confidently, but the rest of the NW corner had only an isolated ____EST, and ____IN. I moved on.
I hamstrung myself (see what I did there?) by entering "ditka" at 39D: Papa Bear of the NFL (HALAS). I mean, yeah, he was the head coach of Da Bears, and he was certainly the leader of them, but he was never nicknamed Papa Bear as far as I know. In fact, he was known as Iron Mike. I further made things difficult for myself down there by entering ditzIEST for 32D: Most airheaded (SPACIEST). You'd think the four correct letters would help, but I had no good entry into the corner.
So fortunately, I finally got going with the excellent GROWUP (9A: Response to a sophomoric comment). Suddenly things started falling. ISOLDE should have been a gimme, but my Wagner operatic knowledge is primitive at best. I much prefer the Italian (Puccini) and English (Britten) composers for opera.
I can't remember how many crosses I had when 8D: It covers bridges, typically (DENTALINSURANCE), but I was excited once I had it in place. Surely now things would go more quickly!
Only not. So... LORENA MESNE LATEN. Those are tough answers. One is legitimate sports knowledge: she is absolutely in the Hall of Fame, and was the #1 ranked golfer, having won multiple titles including the British Women's Open. But not known to me. One is an obscure law term, from Old English/Norman French, meaning "middle". Uh huh. And the last is a made-up word. Well, not officially. But you know what I mean. And I just couldn't bring myself to believe that OISERIVER would be correct. Why is it not in French?
I liked 30D: Students arriving late? (TRANSFERS). And 27A: Joint flare-up? (PRISONRIOT) is very nice because it's a real term for arthritis, and the first misdirection I thought of had to do with marijuana rather than jail. 34A: Goes over the line? (TRESPASSES) is not as clever.
In the NW, ORRIS definitely made things tough. EVAS I've seen before. FIVELOVE seems peculiar. I've never heard it used before, but there is support for it on Google.
Meanwhile, IFINDOUBT is excellent. 1A: Like a hermit (ISOLATED) gets a B from me.
Overall it's a strong puzzle. I just didn't love the solving experience.