I voted as "self-diagnosed" -- but that's really an inadequate description.

I'm an adult with multiple autistic kids who have themselves each been professionally diagnosed... and I share an overwhelming percentage of my personality and characteristics with them. But I'm clearly in the "high-functioning" category, and have managed to reach a certain level of stability and success in my own life; so even ignoring the obvious monetary cost of getting a professional eval, at this point there just isn't much that such a diagnosis would do for me... whereas my kids benefit by having that official piece of paper in their school records; it provides concrete evidence to justify the requests for accommodations which we've submitted on each of their Individualized Education Programs (IEP).

Which is to say, I believe that there are certainly good reasons to go to a professional -- but there are also circumstances which can significantly mitigate those good reasons.