bikerman101,
I have been considering this very same question you are asking at the start of this thread. I currently have a Mustang seat on the 07 ultra, and have had mustangs before and never had a issue or sore butt issue with them, but I see so many people that have the corbin's and love them or love them after X miles when the they break in. As luck would have it I was able to ride a buddies bike this past week for about 200 miles. The bike had a heated corbin seat that has many miles on it.
My report on the corbin seat
The corbin is typically more narrow than the mustang, it does not seem to have the same support under the hamstring area and my butt was sore after about 150 miles, even asked my buddy to stop for a drink just so I could walk around a bit. Had a great ride, but was able to finally make a decision on which seat would replace my sundowners for the cherry and roadking.
Hope that helps