i've actually started using the technique during mixing. its HELPED so much, i think thats the real trick to mid-side.
i did use the ableton utilities, but i a/b -ed with the voxengo plug and i like the sound better out of the voxengo. has more character and less sterility.
one thing i've noticed with ableton plugs, is they are extremely transparent. clean and straight forward. unfortunately, im trying to make my music sound more like vinyl, so any warmth i can induce, the better.
but don't get me wrong, i use ableton plugs constantly!