Looking for a zoom in the 17-70 region. I have the Nikon 70-200 VR so I am very spoilt when it comes to image quality. Now that I have experienced just how good the 70-200 is, I want the same IQ in the 17-70 range. I have had the 18-200 VR and was dissapointed with the IQ from that lens. I have heard really good reviews on the Tamron 17-50, is the Nikon 17-55 a better bet or is the Tamron really as good as the reviews make it out to be. I am not so worried about build (i know the nikon is better there) but Image Quality is very important to me. Obviously cost is a factor.... Currently using a D50 but my D200 is on the way All help and comments are welcomed and appreciated - Thanks.