I know they are not as good as a wire cage. I've turned down applications many times because people wanted to use a tank for long-term. As you'd said above my other post, breeders use them for infants. Well, rescues get in a lot of pregnant moms and litters, too. :? About 65% of my rescue has been litters so far.
I've spoken to established breeders and other rescue owners about the issue of what to use for a nursery many times. I'm not the only one that is afraid of what could happen in wire cages (there's a reason many breeders and rescuers use aquariums and bin cages). I am going to be making bin cages for nursery cages, using cooling racks for airflow along the top and lid. But as I said, they are TEMPORARY and only in the case of newborns and NEVER for transporting. I remove them from the tank before 2 weeks. I am well aware of the risk of tanks, thanks.

However, this is kinda off-topic...
As I was trying to say (poorly, I guess), they should NOT be used generally, especially when traveling, due to the way the heat builds up. I'd be afraid of a greenhouse effect.