So far so good! I candled the eggs and saw veins in all of them. I know they may still die later, but for now the veins look strong.
Sorry for the quality of the photo, my camera doesn't do well in low light.
@zina: Mine's not big either, so I'm not sure why it took so long to heat up. Possibly because the water underneath the floor had already cooled by the time I got to it.
The eggs are on top of a spare bit of plastic. I know some people put them directly on the vermiculite, but a lot also use egg crates to keep them from coming into direct contact with it. I wanted to do that, but I couldn't find an egg crate anywhere. So I used what I had lying around the house.
Humidity has been consistently high. The top of the tub is always dripping when I open it. I think that may have been responsible for the herpstat error. The probe was wet when I took it out.
@John: If I drape a moist paper towel over the eggs will they still be able to breathe? I might give it a try, as long as I know it's not going to smother them.