Sacandium IS aluminum, albeit a high quality aluminum at that. How it rides also depends on what else the frame is made of. Alumininum is light and stiff, which is good and bad. Stiff is good for power transfer, but can be harsh, which is why I believe in the case of the scandium Isis, they added carbon seat stays and fork. I have never ridden such a bike, but now these aluminum/carbon hybrid bikes such as the cannondale six 13 are very popular in the pro peleton, since they can have better power transfer than pure aluminum, but also more comfort.