Wow, this went by fast. It helped that I put in SEALEDWITHAKISS as my first entry. And can I just say that this puzzle shows how stacks can work? First off, there are 6 really solid 15-letter answers, with only one of them using a plural to fit in. And the clues are pretty darned good for those entries also.
16A: Like a hot mess (ALLOVERTHEPLACE) is fine, but 17A: Where everything has been checked (BAGGAGECAROUSEL) is better. I had the first part of the clue entered on its own for a short time until I got more down answers later in the stack.
The lower set of three are better. 50A: They're good for the long haul (TRACTORTRAILERS) is the lone plural, but it fits well. The best clue is at 53A: Game with one round (RUSSIANROULETTE). That's superb stuff there. And no unnecessary question mark! 54A: Like many floor cleaners (ONHANDSANDKNEES) is clever in the exchange of the inanimate "floor cleaners" products for the ones doing the floor cleaning.
So, having put together some fine stacks, do the crosses suffer? Sure, we can pull out some questionable items. 6D: U. wish? (DEG) is a stretch. MILERUN is what the race is called, but feels awkward. Don't we just say the record for running the mile? 52D: I.R.S. employee: Abbr. (AUD) is really not good. Why is that "Abbr." in the clue? Isn't the abbreviation of Internal Revenue Service enough to express an abbreviation in the answer? DTEN is marginal: I like the reference to Battleship, but the mixture of letter and number, not so much.
But in other answers and clues, there's some excellent stuff. 7D: Get a lock on, e.g. (WRESTLE) is a nice piece of misdirection. 39D: Light bite site (BISTRO) was a cute clue. I love 49D: Web content (SILK). Did not expect that direction at all.
Weird to have ELANTRA and TANTRA both in the grid. HANGS is right next to HOMIE, which makes sense. ACUPS is a Huygens entry, IASSUME. And how about 18A: F-, H-, and I-, but not G- (ANION)? That's a pretty clever clue.