Sounds interesting for a program a lot of time for the PhD combo. At least for the school I'll be attending you don't start the OD/MS program until the end of 1st year, with some other requirements that I don't quite know about yet. But the good thing is that it allows people to enter the program only after they have experienced a year.
No, the Prof interviewer I had was part of the OD/MS program at NECO and she said its best to get used to the OD program first, and once you are accustomed to it you can apply in to the MS joint.
I don't actually plan to do the MS since it takes away all vacation time and I'd prefer to go back and visit family instead. Simply personal preference. But if you have the time the OD/MS program is worth it since there is no additional charge and you gain a lot more knowledge. It may also open up some more doors down the road... ie teaching ?