Well, this was one of the stranger grids I've solved in a while. First, there's the east-west symmetry. And the placement of the T-shapes make for peculiar little niches of answers. But I really like it! It's unusual, and therefore interesting.
The theme is T-FORMATION. At first, I wanted to have the revealer at 50A to say something like "form a T..." but the ION at the end just wouldn't work. Finally, I reread the clue, and realized that the BLATANTly obvious T in the middle of the puzzle is actually part of the revealer answer. A further layer of the theme is that the meeting point of each T-formation is itself a T. Clever! You even get a bonus answer in MRT, star of D.C. Cab.
All five of the theme answers are genuine phrases as well. WATER TIGHT is probably the most, well, watertight of the lot, with OFTEN TIMES feeling a little outdated. And does anybody use the phrase DUTCH TREAT? Even "going Dutch," which feels more correct, is out of style. Apparently, one suggestion for where that term came from is in the antipathy the English felt for the inhabitants of the Low Countries: thus, to go Dutch was to be a cheapskate. Some words of wisdom for Frannie as she makes her way through the Netherlands.
Some clues I very much enjoyed: 23A: History is recorded in it (PASTTENSE) is simply excellent. 48A: Alarm clock's purpose (AROUSAL) is a funny way of avoiding the more Huygens-ish (to coin a word) sense of the answer. 71A: Something in brackets (TAXRATES) is clever but not ha-ha funny.
There are a few very nice long answers, including IMPATIENT, SOULFOOD, TINSMITHS. I don't love your random Native American name in crossword puzzles, but ARAPAHOE is much preferable to Ute or Otoe (without making any judgement on the relative merits of said tribes).
Some very unlikeable answers include EDILE, whose presence I've not seen in a grid in quite some time, INUTILE (I wanted "futile" so badly), and NEWER/NEWEL, which are awfully close to one another, if not etymologically related.
And yes, there is a ton of not very nice 3-letter filler answers, especially AWN, MOL, and PUF. But overall, I'm taken by the theme and the way it's carried out. Put that in your bong and TOKE on it!