I have been reading a lot about this lens in these forums, apparently held in very high esteem. This is one of the good glass which I dont have. Is this lens really so good. I have the 17-55 and the 24-85/3.5, which is not in this class, but in this range. The 17-55 is always on the camera, would I find myself using the 28-70 lens a lot too? Anybody has the 17-55 and the 28-70, both ? Which one do you use more ? Thanks in advance.