Long-time readers will remember that I have a wee bit of a pet peeve about looking young for my age. It's a pain most of the time, but I've gotten adept at working my level of experience/age into an early conversation with everybody I meet. I do the same thing during the introduction to any courses I teach, but nobody remembers the course intro, and I don't go overboard in reminding people.
I got evaluations back from a class I taught recently - a class in which I was only two degrees of separation from several of the students. Word filtered back to me that I seemed especially smart and knowledgeable... for my age. I also got exceptionally high reviews for the class in general.
So, was it good that I was mistaken for someone much younger? I'm not sure. Maybe my complex about not being taken seriously is making it harder to be objective and appreciate that there are some benefits to looking young.