Well, I believe the term "Mental Retardation" has been been replaced with "Intellectual Disability"/"Cognitive disability" in most medical textbooks/dictionaries/etc. And I know "intellectually disabled" is considered alright by some, however, others seem to find the "disabled" bit pejorative,
so you end up with "other-abled"/"differently-abled" as pretty common in PC circles these days.
Either way, it's all pedantic and retarded.