We recently published a case study with Unify Square that illustrates the value that an MCM certification (or in this case three of them) can bring in competitive situations. Obviously your own mileage may vary but there is one stand out point in this instance that I think is worth noting. The guys at Unify Square are mostly all ex-Microsoft and held senior positions in the UC product group. You'd think that this alone would be the deciding factor for many customers to select them for a given peice of work on OCS or Lync. However, what happened in this case was that it was having 3 certified OCS/Lync Masters on staff that won the business for them. Powerful stuff - and a great endorsement of MCM and the unique differentiation it can bring. Here is the case study for further reading.
I encourage all the candidates that attend the program to make the absolute most of MCM as a differentiator - and have seen many instances where this has been put to good use. If you consider some of the datapoints from the recent survey of MCMs the value of the program speaks for itself with 80% of individuals definitely recommending it and 70% giving it a 'Very Satisfied' rating. That's huge.