It seems like a powerful & interesting approach - the encoding & decoding circuitry is amazingly simple.
[sum & difference - same either from L/R or M/S]
I tried it out quickly on the Nord G2 demo software a couple of nights ago & enjoyed it!
So, other than being able to vary the level of the side input - for a width control - there seems to be less need for a control of the mid input, though could be interesting/useful.
The idea of separately processing the mid & side separately is very appealing! When the MonoComp comes out, then paired with PEQ - a pair on mid & a pair on side. If I can fit the encode/decode onto a single 1FW panel.. that would make a filled out frame setup

Has anyone been using M/S?