I’ve used M/S micing in two situations. One was capturing an exceptionally wide soundfield. I wanted to add an ambient stereo track of distant thunder, frogs and crickets in my back yard to a song about being in a bayou. Sounds were coming from directions up to 200 degrees apart so I thought M/S might work well. I used a Studio Projects B3 for figure-8 side pickup and an AKG D8000 cardoid dynamic for the mid. It came out with a nice spacious sound, I thought. The song is streamable – Track #2 (‘Lady Of The Bayou’) from https://www.soundclick.com/artist/default.cfm?bandID=1157871
The other situation was my desire to get realistic stereo imaging of 3 harmony vocal backing parts. I set up the M/S pair in the studio. then marked 3 different positions (masking tape on the carpet trick) that were 6 feet back from the mics and 8 feet apart laterally across the floor. I sang and recorded each harmony part separately, standing in a given position for each part, rather like you might position a small choir. That produced pretty stellar stereo imaging when soloed, though some of the finer detail ended a bit buried by the rest of the mix. The harmonies are used in the chorus of this song: ‘Life Song’ (Song #15 on this list) https://www.soundclick.com/artist/default.cfm?bandID=74019&content=songs