Like Magz said, there are pros and cons.
The diagnostic process is neither simple nor short. In addition to the interviews, I was observed interacting with others, both in person and through a one-way glass (which felt weird). Then there were the questionnaires; most are for you, but one may go to your mother (if you tell her it's for a work-related security clearance, she may not have to know the truth). It took a few weeks for the first diagnosis ("AS") and almost six more months for the second ("PDD-NOS + PTSD"). The first one wasn't "wrong" so much as it wasn't specific enough for me, so I got a second opinion (a good idea anyway).
If you want to only self-identify, that's fine. You'll gain peace-of-mind and some insight into your past. If you want an official diagnosis, you may be able to to get some extra consideration in education, employment, and housing, depending on where you live. You may also gain some appropriate prescription medications that may make your life easier.
Personally, if you can afford it, I recommend going for an official diagnosis. Whether you do or not go that far, you might benefit by attending an autism support group in your area (or start one yourself).
(In the interest of full disclosure, I prefer the term "Self-Identify" instead of "Self-Diagnose", as I believe that only medical professionals can "diagnose", while anyone can "identify". No adverse judgement is implied or intended.)
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