This is a crazy, crazy (and three more crazies to get a total of 5 Zs) feat to pull off. The grid is a QUINTUPLE pangram. I didn't know you could do that. There's a little mini-theme going on as well with the addition of FIVEFOLD at 52A.
So... is it worth it? Well, the grid suffers, because each corner is completely isolated, making them all mini-puzzles. Not surprisingly, it's in these corners where some of the more difficult letters are isolated (J in the northwest, W in the northeast, X in the southeast and southwest). Using a random Roman numeral helps to get two Xs (DXIX), while there are more than your standard peculiarities, such as SQFT and DJED.
Still, I feel like on the whole it stands up. The SW corner is well done, with XEROX, OXEYE, MYOB, and SEXY. The middle diagonal section was fun and reminded me of some of David Phillips's crazy themeless concoctions. All of the long answers are strong, including WESTBANK and DOWNQUARK and ACIDJAZZ.
And best of all, it looks like the craziest Scrabble game ever played (if there were that many high-value tiles available). I'm sure some will dismiss this as a stunt, but if so, you have to admit it's a well-done stunt. I'm in FAVOR.
1A: Frequent flier (BIRD) is cute. So non-specific! I was thinking at least a specific species of bird. I give it a B. Strangely, the first answer I entered with confidence was 20D: Jaromir ____, five-time N.H.L. scoring leader (JAGR), in that I don't follow hockey at all.