I picked up a brand new Tamron 17-35 on the internet and it arrived today.... I'd read so much good stuff about it that for £150 I thought I'd give it a go and hope to get a good copy. Well this morning I did some tests on edge sharpness at different apertures and focal lengths to compare with my copy of the Nikon 18-35. First thing I noticed is how difficult it is to focus manually to get as sharp a picture, especially at the edges, as I could... secondly at wide open the vignetting on both lenses is fairly strong. At F5.6 onwards the Tamron is a good bit sharper and equally as good for contrast as the nikon lens (in my opinion anyway)... I made a bit of a b*lls up and dialled some exposure comp into a couple of shots but my instinct tellls me the nikon will go and the tamron is a keeper...pics to follow and a link to flickr for full res versions soon.