I've been on SSD since 05 after 1 session with their doctor. I guess I filled out all the forms correctly and gave a very believable interview. I have MS and it has detrimentally affected my memory (cognitive retardation). Other annoying symptoms also exist but we won't go into those.
Don't like saying this but I suppose it all depends on the luck of the draw.
Power to you people that are still battling the system. Do not give up!