Haven't read through all the replies.... just wanted to add my two cents.
About 7-8 years ago we had Home Depot replace the carpet in our family room. We bought a mid-grade carpet and mid-grade pad. The pad wasn't the best they offered, but it wasn't the worst, either. Well, when the installer arrived, he only had the highest grade pad on his truck, so he said he would install it at the mid-grade price. I was thrilled.
I have plantar fasciitis, and I can definitely tell that room has the best pad. I walk anywhere in the house barefoot, I have heel pain, but when I walk in that room, my pain goes away. It is such a relief.