When I first saw the headline on dpreview I thought it was going to be a replacement for the DX 16-85mm vrII but with a constant f/4. Not being a full-frame boy, that would have interested me (as would a 2.8 version).
Cav, fast glass makes a huge difference depending on you're subject matter. Scenic photos on a sunny afternoon - unlikely to be an issue. Scenic photos at dusk w/o a tripod (or wide shots in a cathedral for example with no flash/tripod supplied) - benefits of these new lenses.
Indoor event shots without flash on a standard zoom - huge difference between say, using one of my standard zooms at 5.6 or my 1.8s/1.4s.
Rob