Funny, I use M/S all the time. Don't know if this says more about me or the average material I get, but I'm just used to it. Really know how to listen to the mix and EQ in M/S. Adding sparkle to the air in the music, without touching the vocals, removing out of phase rumble without touching the kick/bass, etc. I find it very, very useful especially for rock/metal, not so much with dance/techno.
Maarten