I'm pretty sure that the NASA Shuttle Landing Facility (KTTS) has an MLS system. If I recall correctly the shuttle uses it. Also, from talking to a Controller who was a QA Facility rep he said that one of the major reasons that they wanted to implement it was for the multiple and curved "localizer" beams, enabling them to vector multiple aircraft onto the Final approach course and to set up a precision approach at airports that have obstructions on the final approach course.