Bob Katz and I talk from time to time about mixing engineers delivering sessions to the mastering engineer and the various ways of work (Us vs them and vice versa).
Quite a while ago I send him an email concerning my earlier post (which can be found here) about M/S Techniques in mixing, but using it as an effect and how it affects the work of the mastering engineer, if it does at all!
Click here to find out what Bob replied.
Mirror Mixing: The Official Blog 