I, too, found the 24-120 to be obviously weaker than just about all of the other Nikon lenses I have. That makes the 'sharpist' in me reject it. However, it is the perfect 'walk-around' lens. And it is no worse than the Canon 24-105. Will you miss that 20% of quality more than the missed picture? That's what we all struggle with.
Personally, I'd like a tack-sharp 35-105mm f3.5 VR. If they can make the 16-35 and 14-24 as good as they are, this has to be possible...
- N.