After nearly 10,000 miles on my Corbin, I can't find one complaint. If I had to nitpick and find one? Weight. The Corbin weighs about 10 times as much as the stock seat...seriously. Of course, I'm also just being silly, because that weight has absolutely nothing to do with anything. In fact, it probably helps dull some of the vibrations that people have complained about coming through the seat on the FZ6.
FYI, paulinus. I bought my Corbin from another member lightly used (about 50 miles on it) for $185 shipped a year and a half ago. I would definitely recommend scoping out Craigslist and Ebay before you drop $350-$400 on a brand new one. If you can find a deal on a good used one...do it.
Oh, and Yamahamike, I don't know how many miles you've put on your new Corbin yet, but if you're thinking it'll get softer, it won't. When I first got mine, I couldn't believe how hard to the touch it was. I thought, how in the heck can this thing be comfortable??? But, from the very first day-long ride, I was hooked. I think the firmness has a lot to do with the comfort it provides. It "supports" you better than other seats that you sink in to. It's the absolute best mod I've done to the bike and I wouldn't trade my Corbin for anything!