I really like the idea of this as a walkaround/grab and go lens. Right now I have the 24-85mm f3.5-4.5, which is essentially the same things for the first 3/4 of the zoom range. I have a 70-200mm f4 and a 105mm f2.8 (plus other f1.8 primes), so it's not like I'm missing anything within the range. That said, the new Sigma lenses have been very sweet, and with the ability to ultra fine tune their AF with the optional USB dock it could be tempting at a given price point (I'd love to see $849). I may need to rent or at least give it a good trial just to compare things like bokeh and sharpness against the Nikon I have (which I really have no complaints about). It's going to be a question of whether or not I want to spend that much for a walkaround lens.