Received this lens 2 days ago and took it around town and to a baseball game to try it out. Overall I am very pleased with it. The zoom range allows for great flexibility, the autofocus is fast, VR II superb as on other Nikon lenses. While the zoom is not as loose as the early 18-200mm lenses, you do need the included lock for it not to creep if you carry the lens pointed down on your camera. The weight of the lens as other reviewers say is quite comfortable - mine with clear protective filter comes in at 860g, just a touch heavier than the 70-300mm but not something you'd noticed without a scale. Build quality is very solid.
I tested this lens against my 70-300mm f4.5-5.6 VR and the 16-35mm f4 VR and overall I was pleasantly surprised how well the new lens did. Three things potential buyers should be aware of:
1) while the lens is listed as 28-300mm it seems to be neither quite 28mm (the angle of view is slightly narrower than the 16-35mm set to 28mm), nor does it quite extend to 300mm (the 70-300mm gets a bit more enlargement). This is not a big issue in normal use since you'd never know the difference without a side by side comparison, but if you're buying the lens specifically for either extreme of the range be aware of this. I don't have equipment to test so you'll have to wait for professional reviews to tell you exactly what the actual range is in mm.
2) while overall I'm very pleased with the quality - no ghosting during shots I took at the ballgame despite not having Nanocoating - when you compare side by side it is not as sharp as either of the other lenses and has, as is to be expected given the zoom range, more distortion. Again nothing that would jump out at you if you just saw a photograph, but side by side especially at 300mm you do notice that fine details (textures, text) are more crisp when taken with the 70-300mm.
3) The lens very quickly goes to f5.6 - by the time you're at 85mm you're at f5.6. Before buying I had wondered how this lens compares to the new 24-120mm f4, and I suspect that lens is slightly sharper and if you shoot a lot at portrait length you will fine the full extra stop (f4 vs 5.6) to be quite useful. Note I have NOT actually tested the 24-120 since it' not available yet. And of course that lens is about 25% more expensive.
Overall I'm very pleased with this lens, and despite the difference in sharpness this lens will be replacing my 70-300mm in my bag for most purposes - pretty much the only time I'd take the 70-300mm would be to specifically shoot wildlife or objects I know will be far away and I'm trying to keep the weight down (and obviously if you're really into wildlife you should get yourself a faster longer range lens than the 70-300mm).