My statement regarding the MSD certification stands, not so much in that there's nothing else an agency can teach you but more so that there really isn't another recreational level course they offer beyond that. I hold no PADI certifications so I don't really know what they require for the MSD cert, but I know other agencies actually have both written coursework and certain skills that have to be performed to complete the class. My MSD is through NASE and from what I remember the course is somewhat similar to DM coursework but without the responsibility (read as liability).
I do agree though that the MSD certification doesn't exactly qualify someone as a "master scuba diver." Just means more or less that the agency can't take you any further without getting into professional level diving and increased responsibility.
PADI doesn't have a MSD class. Just a certification. SSI is similar. Have the prerequisites to get the certification by taking other courses and you get the certification. NAUI and NASE both have actual courses as I understand it, but for PADI or SSI, there's still LOTS you can learn as a recreational diver if you only had the minimum requirements to get the MSD certification (50 dives, rescue diver, plus shark awareness diver, reef cleanup, enriched air, fish ID, etc count as far as I can see, as well as various "distinctive specialties"... not even required to have diving skills for the specialties from what the PADI site says). So guess it comes down to where you get the cert as to whether it has any value at all.