I am completely open about my autism, and happy with the results. I'm open in interviews, open with coworkers, open with students, open with people I know socially (online or in person). I don't actively tell people right away, but it always comes up, because really, special interest, it'll come up, whether or not I seek out telling someone about myself. Also, they ask about my sensory coping tools.
I've had negative reactions, but almost all negative reactions would have occurred whether or not I was open; they were negative based on my traits, not the word autism. I've had some extremely positive reactions, including some amazing interactions with students. It's always been worth the hard times, and I've gotten many more positive ones.