For me, it is a matter of grammar rather than anything else. The gist of the post will tell you where the person stands, not the exact vocabulary.

I say I AM an aspie but I HAVE ADD. That is because it sounds right. For me it doesn't mean I identify as having aspergers but not identifying as having ADD. Actually I strongly identify with both. If someone wants me to say I only "have" aspergers, I'd actually get really angry. It means that I would want to be separated from having it, and that would be the end of me as a person.

In most cases, grammar is what rules how they say it. I hope we can see beyond that. And also accept if someone actually do identify with their "illness".