Stiffness means that every ounce of energy you put into the pedals gets tranlsated into forward movement, definitely a good thing. The only drawback is that sometimes bikes that are stiff are uncomfortable to ride, since they also don't cushion you from road vibrations. But, bikes that are carbon or carbon/aluminum designs such as the one you are describing seem to do both. Its not just frame material, its tube selection and body weight. The same bike can feel stiff to a light rider and whippy to a heavier rider. This happened to me on my Terry titanium Isis. When I gained weight, the light wsd tubes flexed too much, but when I lost weight it feels perfect. When I was heavier, I preferred my steel bike since it was stiffer, albeit heavier. But now that I am light, I prefer my titanium bike for the best blend of stiffness, lightness and comfort. So, give it a test ride and see for youself what you think of this bike!