The PADI MSD rating is, as everybody has already said, is nothing more then a card and a title. IF that card and title gets a diver to come take more trainging from me to achieve it, then it's worth it. If a diver is on the fence about taking that 5th specialty class and the idea of getting a MDS rating by doing it helps make the decision, great! For me, and I am only speaking for me, my students are encouraged to take the training the need...only the training they need. I often tell them, "you don't need a class for that" and then have the discusion about gaining experience and skill. To me, getting a card and/or rating for the sake of telling the world you are a MDS is all about ego and there is no place for ego in diving.
All that said, DAN has a rating called DES, Diving Emergency Specialist, just a card. If you meet the qualifications (DEMP and Rescue), send DAN 20 bux and you get the card and rating. I'll put on my flame suit while I explain that I encourage my DM students who are lookng to become working Divemasters to get the rating. First DEMP is a great class, second the DES rating look good on a resume and third...I just like supporting DAN.
So I guess the bottom line is, if you like supporting PADI, get the card.
My name is Robert, and I own an SUV.