When I built my Soma Grand Randonneur I was stoked to be able to get a Brooks Cambium saddle with the carved slot. I have a Brooks B17 leather saddle which is great, but applies a little too much pressure in the middle. I prefer saddle with a slot. I also liked the idea of a non-leather waterproof saddle, an important consideration in western Oregon. This saddle felt great by the second or third ride. Brooks says this saddle needs no break in, but it did take a couple of rides before it developed some flex in the middle.
I rode this saddle for many miles, including a couple of 200k rides and several other 100 milers. It always felt great. I thought I had finally found the ideal saddle so I got another one and put it on my Soma Saga touring bike. I was also using the touning bike for commuting so I was getting daily miles on the new saddle. I also did a couple of overnight tours and some longer rides. The saddle felt great.
So off I went on my two week summer tour confident that this would be a comfortable ride. I was so comfortable riding the Brooks Cambium saddle that I only took shorts with a thin chamois and no padding. The tour started off fine, with long days in the saddle and no discomfort. It wasn't until the second week that I noticed I had developed a sore where my left sit bone hits the saddle. I treated it, but it was getting harder to ride. At this point I hadn't really implicated the saddle. Then at camp one night I meet a women bike tourist who had the same saddle in a women's specific model. I asked her how she liked it. She said "It's great but it has absolutely no give under the sit bones and it's starting to hurt my butt". I checked mine and realized she was right. While the middle section around the cutout was nice and flexible, the rear of the saddle was hard as a rock. This wasn't a matter of break in. I already had months of riding in on this saddle. The design is such that it will never get any softer under the sit bones. I had a layover day in Seattle which allowed me to go to a bike shop and buy a the thickest padded shorts I could fine. I was able to finish the tour, even though it was still somewhat painful in the saddle.
After returning home I removed the Brooks Cambium saddles from the two bikes that had them and started trying out my older saddles to find something I could ride. I have a Terry Fly, and a couple of Selle Italia models, but the one that felt the best was the Brooks B17 leather saddle. This well broken in saddle has just the right amount of flex under the sit bones. At one point, thinking I was healed, I put the Cambium back on the Grando and did a long ride. It was fine during the ride, but the next day I found the saddle sore was back and I could not ride in that saddle again. I went back to the B17 leather and could ride again.
So for me the verdict it in on the Brooks Cambium saddle. It is too hard under the sit bones. It fits great, and is very comfortable even on long rides, but will wear out my butt after prolonged use. The construction seems to be such that it will never develop any flex in the rear under the sit bones. Leather saddles on the other hand will stretch and provide the flex you need under the sit bones. With that in mind I have purchased a Selle Anatomica and am just starting to break it in. Say tuned.