Have waited a month to review this, as wanted a genuine comparison, from my D90, using the 16-85 VR lens.
At up to ISO 1600, f5.6 and above, up to 10"x8" prints, you will hardly see any difference in image quality, but push the D7000 and it shows its true worth. The ergonomics, layout and handling are all better than the D90, and the many extra features over the D90, are extremely worthwhile, giving a new dimension to your hobby, and a great expansion. Some little things are amazing, like the rear infra red receiver for remote, mirror lock up, very fast motordrive for a consumer model (jpeg), (slows considerably in RAW), and the virtual horizon is a great addition (need to custom select for viewfinder, which is also larger and brighter as well), interval shots, and nearly half as much battery life as D90, great.
One worry I had, prior to purchase, were the reviews of over exposure, it is no different to the D90 ~ result.
I mainly take stills, but the video is again better than the D90 + masses of storage with the 2 memory card slots, and a 20 minute burst rate.
Focus is better and quicker, especially with older lenses, and the low light capability is excellent, all in all, Nikon at its best, delivering a genuine enthusiasts DSLR, with not too high a price tag, and if any D90 owners are thinking it isn't worth the upgrade ~ IT IS. Add in its better build quality and weatherproofing, I love this camera, and will be very happy to use it in the coming years.
2 months on, I'm using this now with a 17-55 non VR, and 70-300 VR, image quality is very good indeed, better than I anticipated, and again must mention this camera is excellent in low light, unbelievable at times!!
Another 6 months further on, Nov 2011, and the D7000 has been on a trek around America, with the above lenses. I'm still very impressed with the capability of this camera, and am so pleased I swopped from the D90, I can't see me getting rid of this camera in the next few years, unless bodies improve dramactically, as I feel the Camera and myself are at one, and I think that says it all. HIGHLY RECOMMENDED for enthusiast level, well done Nikon!!