The grill temperature was around 600 when I put the pizza in. I left the grill open longer than I wanted though, so a lot of the hot air escaped. This is a problem with grilled pizza that I will have to work on. I do not yet have an IR thermometer, so I'm not sure exactly how hot the stone itself was, but since it's right over the propane burners that were all set to HIGH, I'd guess it was pretty hot.
I think I'm a little obsessed.