I find it very hard to tell the difference of bitrate when I'm listening. I have only noticed it when I picked up a set of Sennheiser HD 650 headphones for editing my tracks.
I noticed one hypnotherapy recording company using a bitrate of 56 kbps and the low-quality bothered me a bit. I want to keep my bitrate as low as possible so everyone gets the best download speed and ease of storage. Most of my files are 128 kbps but I am finding that 96 kbps seems to work fine.
Can you tell the difference? Do you care?