The 100mm is said to be one of Hasselblads best lenses together with the 180/4, the Biogon and the Superachromats. I have no real experience with it (played around with a 100/3,5 CFI at Photokina though), but have seen a lot of pictures made with it. I like its angle of view very much, which is visibly narrower than that of the 80mm. At the same time, it is about the same size as the 80mm.
Q.G. who is not around here anymore said that the optical difference between the 80mm and 100mm is narrow in real life if both lenses are stopped down.