All-leather saddles such as a Brooks will break-in just like a good pair of leather boots. My Brooks Pro that I had on my old Raleigh Professional Mk IV was hard as a board when new but broke-in after a few hundred miles (and a road race in a thunderstorm). That's not to say that your ass doesn't "adapt" as well. Just make sure your bike is sized and set-up properly or no saddle will be comfortable.