78 is only comfortable to me if there is a breeze circulating (like a ceiling fan).
The rooms at the values, and if I remember correctly, the mods, do not have fans. I cannot sleep when I am hot. I DO agree that 78 would probably feel nice and chilly in the stores/restaurants when coming in out of the heat on a park day.
Don't know about the other mods, but just got back like 3 weekends ago from Coronado Springs and in the new refurb. room I stayed in had a terrrific ceiling fan (and the a/c worked perfectly too). The rooms there are super nice.