The Corbin that came on my K75S was a thing of beauty, but it felt like it was padded with cement. It was fine for commuting up to 50-60 miles and errands around town, or an afternoon exploring the twisties.
For munching miles, it was tolerable the first day, but it was a short day, less than 400. The second day it was merciless punishment and for the rest of the trip it sucked every bit of pleasure out of riding. My first(and only) trip with that seat was to bring the bike from Dallas to Western New York, 2000 miles in 4 days. I had hoped to do it in three days which was a piece of cake for my BMW comfort seat, but after the first day I had to stop and take a break at every gas stop, and even at that could barely make 600 miles a day. The last day I didn't even want to ride, but needed to get home.
I bought an AirHawk seat pad, and used it whenever I took the bike out for a ride longer than an hour. That pad was amazing in how it made the seat usable, but it felt kind of squirmy under my ass.