I bought several of the MCA half-speed masters. IMHO, none were bad, neither did any of them sonically wow me, including the Pettys.
In '80, CBS began pressing 1/2 speeds. Vinyl was ok, mastering was ok, DR was ok. IMHO, few if any in that series sounded fantastic. I bought most of them. Boston, Memories, Guilty, Streisand Hits II, The Way We Were, Stranger, 52nd, Born to Run, Darkness, Miles' Man w/Horn, Daniels' Million Mile, Tony Williams' Fear of Flying, Heavy Weather, Chorus Line, and mono Yardbirds' Roger the Engineer. 3rd World's You've Got the Power was digital Mastersound release, not 1/2 speed. It sounds far better on regular vinyl. Regular LP had better bass, but noisier PVC.
MoFi and Nautilus 1/2 speeds had far better vinyl. Far better mastering, too, albeit not a flat transfer by any stretch. Direct Disc Labs vinyl sounded like popcorn. Several titles had manufacturing defects.
Moby Grape (1st) UK mono
Super Sonic Sounds - Sun Ra
Notorious Byrd Bros. & Sweetheart of the Rodeo - Byrds UK 2 LP BEST ANALOG!
California Soul - Tamba 4 unreleased LP by Brazilian jazz band, record store day exclusive