From my own personal experience with this "illness" and from what I know from my knowledge, I feel that the "autism spectrum" is something that has greater variety than many realize. I myself have been long suspected of being "on the spectrum". However, there are many things about me which truly do not seem "autistic". I have the solid ability to converse and relate to others. To many, they would think "not autism" because I have not been impaired in interpersonal relations. However, although I have some ability to function in the world, I suffer from extremely poor executive functioning (the one trait which has been of serious detriment to me). Also, I have a lot of bizarre fixations and fantasies such as aliens, having strange powers, being an alien, being able to transcend to higher realities, a strong interest in out of body experience, etc., all things that would suggest schizoid thinking/mental illness. Also, I have a tendency to fixate/perseverate in general which suggests autism only I somehow avoid my "fixations" around other people. Additionally, as a kid I frequently made a lot of "off the wall" remarks and despite all of this, most people don't see anything wrong with me when meeting me and I rarely get odd looks or attitudes.
Now to throw everyone for a loop here, much of this has not been of detriment to me in my life. I am currently attending college and am doing reasonably well (although I have had a few difficulties recently) and function quite well socially. My strange ideas have kept me from really seriously feeling negatively about myself and my issues (as I convinced myself I had special powers or was some type of greater than human being). My fixations have served me well as whenever I "perseverate" on a specific thing, I tend to do very well with it, far beyond my peers. My executive functioning issues only kick in when I am doing something I don't really care about so it serves to keep me from getting into ritualized jobs. Maybe despite all of this, I'm not mentally ill, but merely very mentally different (with a surprisingly normal outward appearance). Maybe many of us here are really in the same boat on this