I have one - used it in my film days and kept it for an eventual full-frame DSLR, which I now have in form of a D800.
NAS is making me lust after the 16-35 f4 but I can find very little wrong with my 18-35 other than a bit of corner softness on full frame as previously mentioned. It is a light compact lens that lives in a corner of my bag for those occasional situations where I need it.
The extra 2mm at the wide end of the 16-35 is significant if you shoot big expansive landscapes. the 16-35 is also lightweight but nearly twice the physical size of the 18-35 - and at least double the price.