As others have noted, it doesn't have nearly enough ventilation. And the other thing I always think about when I look at a coop design is how easy (or hard) it would be to clean. Unless the back side of this coop opens up completely so you can easily rake out the bedding, etc., I don't think this design works in that department, either. But, those are two issues you could fix by modifying the design.
The other thing I think is good to have are roof overhangs.