This is a very good lens.
Initial impressions:
Thus far I have been able to test it on my D90, which is a DX-sensor camera (as opposed to the full-frame pro cameras such as the D3). Please note that this lens is designed mainly for FX shooters. I plan to test it on my D3 camera later.
When compared to the well-made 18-55mm kit lens, this lens shows somewhat better sharpness at the same aperture. Overall I would conclude that this lens is sharp, but not "perfectly" sharp.
Combined with the fact that it collects more light (f4 vs f5.6), the fact that it has Vibration Reduction II, and the fact that it zooms to 120mm, this lens offers a lot of features as a "go to" general purpose lens for FX shooters (and DX shooters as well).
For DX shooters, the 24mm wide-end will not always be wide enough. For FX shooters, the 120mm long-end will likewise not be close enough. The f4 max aperture is good, but again, some shooters will need or want f2.8 or faster.
This is a lens that makes a lot of compromises and does so intelligently. It is not the perfect lens for any situation. But it is a lens that will take very good, even marketable pictures in a wide variety of situations.
Pros shooting for money will usually bring a bag of pro lens, and this lens will not change that reality.
But vacationers, pros who cannot always bring a huge bag, and photo enthusiasts would be well serviced by this lens.
UPDATED: I have now shot with the lens on my D3. In the center of the frame it is almost identical to my 24-70 2.8. Excellent center sharpness. It is a bit less sharp in the corners, but I am very impressed.
Final verdict: It is a little bit too expensive, but I have upgraded it to five stars instead of four stars based on its center sharpness. I consider it a low five, high four... depending on your camera, your other lenses, and the size of your wallet.