I have two of these beds, one for each of my girls.  They are outdoor beds and exposed to a lot of humidity.  I see zero mildew after being outside for months.  They are a little noisy and tend to pouf up when my dogs get in them, which made my dogs stay off of them,  so I unzipped the zipper so the bed would lay flat.  After I did that, my dogs climbed right onto them.  I often throw a blanket on top of them to make it a little bit softer for them.  It is easy to wash a blanket, not so easy to wrestle with a large dog bed cover.

Pros: Definitely a mildew resistant dog bed
Cons: Needs to lay flat without having to unzip the zipper.