Keep in mind, I'm currently only 10 weeks along, not even done with the first trimester yet and hadn't initially planned on telling anyone until we passed that milestone.
Anyway, my PI (who I think I did previously refer to as pretty damn amazing) was actually excited when I told him I was pregnant. I wasn't quite sure how it would go over (though there is another post-doc in the lab who had a baby 2 years ago so I wasn't the first in the lab to have to tell him such news), but he pleasantly surprised me. Suddenly he was giving me all this advice (taken from his wife's experience, but of course) and telling me how the birth of his daughter was one of the best moments of his life.
And yes people, I count my blessings every day that I managed to find a lab that..
a) works on something I am very interested in
b) is run by such an awesome person.
Now, I just have to figure out how to tell him that I plan on taking 3 months off once the baby is born.... :) But I think I'm going to wait a little for that announcement.