Boy, that SW corner was a toughie! Is it just me, or was LTGEN (45A: Geo. Washington was the U.S.'s first) not what you were expecting? I don't like the way SNAP is clued (55A: Get the picture), and CITRON (39D: Fruit historically used for medicinal purposes) isn't typically used as a fruit name in English, is it? We had "fanBOAT" for quite a while instead of AIRBOAT (42A: Everglades transport), and SCOURGES (38A: Burmese pythons in the Everglades, e.g.) took forever for me to think of, even when I had "___URGES." But, 'though it took up close to half the time, it did eventually come together, and I was very happy to see the "Congratulations!" screen. Whew!
The rest of it seemed a tad on the easy side for a Friday, but not so much so that I'm going to mention it here in the review. :) PANGAEA (32A: It underwent a long, massive breakup) went in without crosses, and Frannie finished up the SE corner before I even saw the puzzle. THISOLDTHING (36A: Question asked modestly in response to "That looks great on you") (or, to "That's some dress you got on there.") made us smile to think of Violet Bick.
Nice little inner theme of RIOT (22D: Real card), YOURETOOMUCH (27A: Comment to a card), OHGROWUP (3D: Response to a puerile joke), and the paired "Took command of" clues (1D: LED & 49A: SPEARHEADS) were fun.
I felt a confidence beneath the grid, if I may, and was skillfully misled by nouns that I mistook for verbs, as in 11A: Book deals? (BETS) and 36D: Wear without straps (TUBETOP). I smiled at 7D; Tag base, perhaps (TREE), and was "sports fooled" by 21A: The Mariners, e.g. (PROBES), and "audio fooled" by 26A: Studio mixing equipment (PALETTES). D'oh!
Didn't love SLUED (24D: Swung around). "Nautical term," eh? Well, I've never heard of it. And speaking of nautical terms, EXHILARATE, while being an excellent word on its own, seems a little strong for 15: Buoy.
Overall, I'd say this gets a thumbs up. It was challenging, and it had many good pieces.