Some condensation will happen but it's minor unless it drips right into a feed bucket. That's the only problem I can think of.
Mine is open-air hardware cloth on all sides so the rain blows inside. Working on placing tarps strategically on two sides. They'll still have 80% free-air ventilation and a chance at breeze. I also free-range them nearly every afternoon so they can run to the woods for coolness.
A good point there -- with adequate ventilation in certain climates a little condensation is no problem.
I have a 3-sided shelter on the roosting end of my Open Air coop but I add a tarp to part of the 4th wall for hurricanes and winter. Some weather blowing in is not a problem as long as the roost area is dry.