3 days in the Explo, I just like a child in a candy store, for there are too many things to see. Every country presents their unique culture and goods in their pavilion.
If you want to go there, avoid the summer holiday. Best time to photo the pavilions is at dawn when the light is on and the sky still bright enough.
I think the six months Expo time is too short and it is time to revise the Expo Regulation.