Thanks, guys -- it's going very well. I still have to pinch myself to know this hasn't been just a dream.
I wet the floor twice a day, except on watering days, so the humidity stays between 70 and 80%. Watering is such a pleasure now. I can water with abandon, and the plants seem to be responding well.
Depending on where in the greenhouse, the temp is 55 - 58º F at night and about 70 (where I have it set) during the day. On days when the sun is out fully and the temperature has been in the 50s, it's gotten to 78 in the greenhouse.
I'm not sure yet, but I don't think I'll need shade cloth. There are big trees to the east and west of the greenhouse, and the triple-pane glass is coated, so although there is a lot of sun coming in (on sunny days), it doesn't seem to be harmful.
I'm learning the different "micro climates" in the greenhouse, and have moved plants around accordingly. Places I thought would be cooler turned out to be warmer, and the area I thought would be warmest extends a little further than I expected.
It is really a great place to be, and I would encourage anyone who is thinking about building a greenhouse to take the plunge! It is worth it.