As the question was asked here, on WP, I answered "aspie". I.e. when I'm in a group that consists predominantly of others on the spectrum, plus people who are familiar with the terms.
If I'm talking to someone who I doubt has much of a clue, I generally will say that I'm diagnosed with "Asperger's syndrome". When I see that they don't know what I'm talking about (quite typical), I'll say I'm autistic - which they've probably heard of (unless they're exceptionally stupid).
I find "Aspergian" quite affected, twee, supercilious? (Although I have used it, once in a while).
In writing (and sometimes in speaking), I'll use ASD. I find myself uncomfortable if I use AS, unless it is utterly clear that I'm not referring to "that organisation which must not be named".
I'm not just a regular, ol' human being - I'm a aspie.
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"Striking up conversations with strangers is an autistic person's version of extreme sports."
Kamran Nazeer