Wow, this was a complicated theme. I knew something was "up" when I wanted to put ALLI[NTH]EFAMILY in at 17A: Groundbreaking 1970s sitcom, but couldn't fit it in. Was there a rebus? What were those grey squares doing there? In fact, because of that, the NW corner was a blank for me with the exception of MPAA at 1D. I couldn't remember John Travolta's character's name from Saturday Night Fever: I got him confused with Danny Zuko from Grease. So MANERO gets a B- from me.
I wandered through the grid, not getting much until the SE corner, where EROS, SASSES, and the questionably clued 54D: Heads of the black community? (AFROS) - I was queebish about entering that with no crosses, but it turned out to be correct - led finally to getting HIGHERPOWER, and breaking open the theme.
The theme itself is extremely well executed. Note that the NTH (moved above the theme answer, just as an exponent should be) is split in three different ways in the overall answers. Thus, the sitcom has the break between the N and the T, while EVE[NTH]HORIZON has it between the T and the H, while ELEVE[NTH]HOUR is not split at all. All three theme answers are well accepted phrases, although I suppose you really say "at the eleventh hour" but I can let that slide.
And then the words containing the various NTHs are strong answers as well. 43A: Column that's beside the point? (TENTHS) is the best, but 25A: Threesome in a quarter (MONTHS) fooled me for too long. It's almost a shame that the clue for 25A couldn't also have worked in the word "column".
There are two pairs of 10-letter down answers in the NE and SW, both of which are strong as well. PEASHOOTER is my favorite. The rest of the puzzle is remarkably choppy, with a ton of short answers. I would have preferred 66A: Effeminate (FEY) - another queebish answer - to be clued to Tina, who is not in the least bit queebish in my book. (Did you ever think that you'd read a review that included the word "queebish" not once, but four times?) And is HEF really his bunnies' beau? Not anymore, I hope.
My favorite clue-answer pair is 32D: Bar entertainment? (LIMBO). Nice stuff. Overall thumbs up.