I bought one the Marine rack for myself and the white for my sister. We both had the same problem. Water pools in the bottom layer and molds. Yes, I empty out the water that accumulates throughout the day, but some water stays there. We both have "retired" this bottle rack to our cabinets.
The design is beautiful and perfect for a modern kitchen. I now have The First Years drying rack and while it clashes with overall "tone" of the house, it is more practical. Luckily, I breastfeed so I do not have to use the rack too often except to dry the pump parts.
I think this product fills a void in the market (come on designers... give us some non-baby looking modern products), however mold/mildew is not worth it to me.