I received my two ET-73s on Friday. Put one together and tried some of the settings. Can't wait to put it to use for a Father's Day Pork Butt. This will be my first attempt at low-n-slow with my new WSM, as I didn't have a real thermometer before. Have done some steaks, corn on the cob, potatoes, and chicken breasts, but not the long, unattended BBQ.
The probes are not to be submersed in water, but it is safe to wash them. Based on this, I doubt any condensation that results from hanging one from the dome will cause a problem. I think of them as air-bake cookie sheets -- you can wash them, just don't hold them under water. Since the unit isn't sealed, it may force air out when under water, which then makes it very hard for the water to get back out.
Geordon