
The biggest drawback is that it is very difficult to get the temperature where you want it. The warmer itself warms to something like 108, which would cook your babies, so you need layers of padding in the bottom. The rehabilitator had put several inches of toweling and was able to maintain the temp at 94. I had to try many combinations, finally settling on one thick dishtowel, topped by 10 one-third sheets of Bounty paper towels, the ones that can be torn off in thirds. This kept the temp between 92 and 94, which is just about what I want for newly-hatched babies. You will want to do all this long before you need the brooder, as it took hours of fiddling to get it just right.
I leave the small lid open for ventilation, plus I don't close the large lid all the way (mine is very hard to open, so I don't want the hassle every two hours!). The large lid is propped open by the cord of the thermometer probe. I put a small cup like you get at fast food places for ketchup, etc., filled with water for humidity. As the baby gets bigger and I need to lower the temperature, I will just crack the lid some more.
So far, it is working just fine. I am handfeeding an Owl hatchling--it was hatched out by my Societies, but after they squashed a Strawberry baby, I wasn't going to let them have this one! Its parents are fawn hen and split/fawn cock, so this baby could be fawn--it is certainly very light.