Looks like cost and perhaps weight of the unit was a concern, but I would've loved to see something larger than 1x2s in parts of the structure for extra strength, as coops always end up heavier than first estimated.
Ventilation seems to be adequate for the size of the coop, assuming the louvered window is completely open with only wire mesh behind it. Same goes for the smaller slots near the top of the other sides.
The pop door could possibly use more secure hardware if raccoons are a concern, though a small padlock or even a carabiner could be used to do that.
I don't see mention of a roost. Placing one could be a little difficult in this set up if trying to avoid a draft going past the chicken's heads.
