I'm loving this lens, I really am. For $500 range, this lens is on par with the Nikon professional line of lenses, sans the wallet breaking prices. Yes, you are getting a plastic body (albeit high-quality) instead of a metal body, and it's a variable aperture instead of a constant one. But really, the differences end there. The lens is incredibly sharp from 70 up to about 200, where it tapers off some. Also, it has a curved 9 bladed aperture design which gives a pleasing looking bokeh. By comparison, the 17-55mm 2.8 gold ring lens has 7 curved aperture blades. Not necessarily the fairest comparison, but just wanted to note some of things you get for what you pay.
Like all telephoto lenses, the 70-300 is sizeable at 745g (1.6lbs roughly), and with the attached lens hood, it's hard to escape attention. I've gotten many "now THAT'S a lens!" comments while using it. I guess all my other lenses must not be real or something. However, I use this on a D80 with a battery grip which really helps balance the lens out and makes it far more comfortable to hold. Generally the weight of the lens is rested on my left hand under the barrel which makes it feel far lighter, but the weight still adds on my neck, especially if I use it with my sb600. Getting an aftermarket soft material neck strap has really helped out a lot, and gets me away from the large Nikon "steal-me" strap lettering.
The real meat and potatoes of this gem of a lens is the second generation VR technology which is rated for a full 4 stops of shaky, wobbly hand stoppage rather the 3 stops offered on the 70-200 VR. This has been tested by many independent reviewers and proven to be true. If the opinion of one non-professional reviewer can be added to that, I'm here to say I wholeheartedly agree with them. I've gotten shutter speeds down to 1/10th hand held and still come out with relatively decent shots. While this won't help you too much with sports shots, since you should be using a relatively fast shutter speed anyway, most other shots will benefit from it.
So uses? I've found this lens to be great for outdoor sports shots, daylight candid and some nature shots. It's also makes an excellent portrait lens under studio lights in the 70-105 range. Due to the slower aperture, it isn't terribly useful for indoor sport shots. The 70-200 2.8 would serve you better. Shots of the moon are also fun to take, but you'll need to do some sharpening in post if you take the shot at 300 where the lens is a bit soft, and will need to stop down a bit to correct that. Vignetting as expected is non-existent, but there is some CAs on the far telephoto end. These are correctable in Photoshop however.
All in all, you get second generation VR, 9 bladed aperture for pleasing bokeh, sharp optics, and relatively good build construction on par with the gold ring 12-24 f/4 (a professional lens with a plastic body), and being a non DX lens (doesn't have a reduced image circle) so you get to take advantage of the sweet spot. Drawbacks' being it is heavy, variable aperture, soft 200+ and does suffer from CAs at the far end. However, it is definitely a lens I will have for many years to come, and one I can confidently recommend to anyone.