Given the expense and apparent failure rate of some MB transmissions, it might be worthwhile to consider using the recommended fluid. The dealer has it, or you can look at http://www.***************/
Some have suggested doing an analysis on the used fluid to check for internal deterioration.
Since dealers have a checkered reputation on how to care for these transmissions, it might be worthwhile taking your car to a recognized and reliable independent for the first fluid change to establish a baseline, then doing it yourself thereafter.