I have to admit; I didn't entirely get this theme. After thinking about it for a while, I emailed Jim. Here's what he said (and what he meant).
ME: Did you understand what's going on today?
JIM: FLYING BUTTRESS -> FLYING BUTTER. (What, you couldn't figure that out?)
ME: But the GENDER NEUTRAL revealer?
JIM: Cutting off the ESS. (Again, isn't this obvious?)
ME: But but but, if you cut off the ESS, wouldn't it be FLYING BUTTR?
JIM: There's the "female-sounding" hint in the clue. (Stop being so picky!)
ME: Taking the ESS sound off makes it sound more like FLYING BUTT than BUTTER. (Tee hee.)
JIM: Yeah, I'm more lax about these things than you. (Just enjoy the frickin' puzzle, you hoser!)
Even if the theme didn't resonate with you, there's a lot to enjoy in the fill. TAX RETURN and STRONGMAN take up the long down slots, and there even more goodies: CAR RACE, ATE CROW, CATNAPS, MEEMAW, even KREWE (Mardi Gras term for "crew").
There was a price to be paid, though, in ENS, NNE, SSS, SYN. These are minor offenders—I wouldn't even bother pointing them out for an average constructor, but Amanda and Karl have the technical skills to smooth some of them out.
I'd have focused on that west region. With a couple of hours work, SSS and SYN could have been history. Not entirely sure what would solve the problem, but shifting around the black squares at the ends of BELIEF and NEW would have been a good start.
Overall, I liked the theme idea — BLOWUP MATTER as TNT is hilarious. (I'm a huge Wile E. Coyote fan, what can I say?) But I would have preferred not having the GENDER NEUTRAL revealer, in favor of adding a fourth themer.
I probably could have figured out what was going on. (Probably not.)
ADDED NOTE: I had been thinking along the lines of LIONESS -> LION and STEWARDESS -> STEWARD: simple ESS drops. Astute reader Seth Cohen points out that the theme makes more sense, if you think of it in terms of how WAIT(RESS) changes to become WAIT(ER).