I'll admit I've only played around a little with mid/side... but I abandoned it pretty quickly because it sounded expansive in headphones... but created this weird "hollow' and moving feeling as you moved your head around the listening position on my mains, as the side phase-reversed recordings got louder or softer depending on which speaker your head was closest to, and it sounded pretty awful in the room. It's possible there was something I was doing wrong here, but... if not, my takeaway was this was only really a good approach for headphone listening, when it was even remotely close to a near field source. I hear it's better as a distant mic on a large stereo source, like a choir, or something, but I can't say I've tried.
