I actually just "came out" to a couple of coworkers just the other day and they were *really* supportive. I decided the time had come because I was occasionally showing up late for work (mornings are the worst for me) and was always leaving my desk for the bathroom. Both coworkers thanked me for my openness and said they would do whatever they could to accommodate my needs. I knew they were nice, but I was still suprised by how well they reacted!
Otherwise, the only people who really know are my immediate family, my partner, and two friends (one who is in the process of being diagnosed with IBD). While I don't try to hide it, it doesn't come up that often. I'm all for making it less taboo, though my partner seems to be more secretive about than I am, because he's worried about embarrassing me. Like, he's told a couple mutual friends that I have a chronic illness, but refuses to tell them which one! I told him I really don't mind people knowing, but oh well... It's better than having him blab it to the world I guess.