I'd say today's puzzle is pretty much how you want a Monday puzzle to be. It's a fun theme with a surprise revealer, and smooth fill for the most part. I only regret that Dr. Haight's great sense of humor has less leeway on a Monday because the clues have to be relatively straightforward. We do see some of it in clues like 57A: "____ your piehole!" (SHUT).
So the revealer is ONTHEBENCH. I feel doubly bad for our constructor that Mr. Charlson's excellent Friday puzzle of this past week played the same game with the clue "Their players are often benched," leading to the answer "pianos." Today, we instead get 48A: Herbie Hancock or Chick Corea (JAZZPIANIST). That's certainly the jazziest of the theme answers, on several levels!
But there are also several snazzy answers in the fill, including 7D: Boat you might shoot rapids in (KAYAK), and 40D: Leave at the altar (JILT), which always reminds me of Anthony Trollope, and his frequent admonishment of "There's many a slip twixt the cup and the lip." Of course, the right people almost always do end up together in his novels. But not always...
WEREINLUCK makes good use of a long down answer with a fun colloquial answer. We really need a better name for these sorts of uttered phrases which are so much more common nowadays in the NYT puzzle. Any takers?
There were a few answers I was NUTSO KEEN on, including OSSA and ICARE ("Words of empathy"? I feel like if I said that to somebody they'd look for the easiest way to exit the room). But on the whole, we'll give this puzzle a nice thumbs up.