The D7000 is Nikon's best all-round camera as of late 2011. If you can't get a particular shot with this thing, you probably won't get that shot with any other camera at any price.
You can spend as long as you want tweaking just about everything on the D7000 to get it set up exactly the way you want it. Then, when you lift it to your eye, it gets out of your way and just works, exactly as it should.
Beyond the D7000 (about \$1050 a month ago, but you might pay a premium at the moment because the Nikon factory is underwater), you have to spend exponentially more cash to get increasingly tiny image quality improvements that almost nobody will notice. If you want a visible improvement in image quality, the next digital step is a $20,000 Phase One (almost nobody can tell a \$700 DSLR's pictures from a \$5000 DSLR's pictures without checking the EXIF data). Two significant steps up in image quality gets you an old-style view camera that takes 4"x5" sheet film; everyone will see the improvement from that step, but large-format film is an artist's format and is not nearly as convenient as digital.
Sensor: The D7000's DX-size (1.5x crop) sensor is Nikon's second-best, trumped only by the full-frame chip in the D700 and D3X. It is a 16 MP CMOS design and can be cranked from ISO 100 to 25,600 (although it does get a bit noisy at 3200 and up). As with most cameras, "16 MP" really means 8 million pixels of green, 4 million of red and 4 million of blue in a Bayer pattern. So while it's not quite competitive with 35 mm film on the resolution front (not that megapixels matter much anyway), it's enough for sharp poster-size prints, and is far superior to most 35 mm films and most other DSLR sensors in terms of noise and sensitivity.
Fast: It's autofocus is both quick and smart. 39 focus sensors, 9 of which are the good cross-type ones, combined with smart electronics, mean that it rarely takes more than a few hundred milliseconds to lock and fire. And I rarely have to take it out of fully automatic focus mode; it's surprisingly good at picking the right focus points without any coaching.
Meter: It has the best meter of any Nikon camera, and Nikon's Matrix meters are (generally speaking) the best in-camera light meters around. There are 2016 individual meter elements, and it meters in full colour. The meter seems to interface seamlessly with the flash, both meter and flash take focus distance information into account, and the meter's resolution is good enough that it can track moving objects and tell the AF system to shift focus points accordingly.
Ergonomics: It's ergonomically excellent- comfortable to hold, the controls fall right under your fingers, and everything's right where it should be. All the key controls (program shift, exposure compensation, flash compensation, white balance, image quality, depth of field preview, ISO, aperture and shutter speed if needed, and several others) are mapped to either the thumb and forefinger command dials, or a button plus the dials; there's rarely any need to sort through menus while shooting. A few of the buttons can be customized, if you so choose. This is what really makes the difference between a "pro" camera and a "consumer" one- whether the necessary controls are right at your fingertips, or buried under many levels of menus. Plus, the weather-sealed magnesium body just feels more solidly built and less fragile than the plastic bodies of lesser DSLRs.
Custom modes: U1 and U2 modes allow you to choose, save and instantly recall complete banks of camera settings. Going from sports to landscapes is now just one click of one dial; it used to mean picking up a different camera or spending a few minutes poking through menus. The P/A/S/M mode retains all its settings when you flip back to it after using U1/U2, so you can effectively switch between three different cameras just by turning that one mode dial.
Storage: Two SD card slots can write as fast as you can shoot, and let you keep a running real-time backup of everything you shoot- a corrupted card or accidental format won't wipe your day's work. Good SD media today is only about \$2-\$3 per gigabyte, and performs just as well as expensive CF media.
Aspect ratio: Like all 35mm film cameras and most DSLRs, the D7000 uses the inconvenient, obsolete 3:2 aspect ratio (width:height). The 4:3 ratio used by compact cameras, or the 5:4 ratio of large-format film, are a much better match for most subjects, and need much less cropping to be printed.
Mode dial: The P/A/S/M exposure modes share an indexed dial with the U1 and U2 custom-everything modes. So if you're using U1, and you had programmed U1 to use P (pro auto) exposure mode, you can't suddenly decide that you need A (aperture priority) mode for a particular shot; flipping to A will change all the other settings back to what they were last time you used P/A/S/M. The exposure mode control (P/A/S/M) might be better of as a "hold this button, then spin the command dial" control in the same manner as white balance, meter mode, ISO or image size.
Auto and Scene modes: These are quick snapshot modes, and the kind of shooter who would use them will choose the exact same sensor in the smaller, lighter and cheaper D5100 package instead of getting the professional D7000. The Auto modes waste two slots on the main mode dial that should have been U3 and U4; Scene takes up a third. Scene mode (pre-set parameters for portrait, night, action, etc.) could have been quite useful if Nikon had provided the ability to save tweaks to these settings, and had left all the usual manual override controls enabled. Instead, these modes lock out most of the manual overrides that are the very reason you chose a D7000 instead of a D3100 or D5100.
Video autofocus: The D7000 has to retract its mirror to expose its sensor, meaning that the phase-detect focus sensors are unusable in video mode. It does have a contrast-detection mode that makes it hunt back and forth until it finds focus, but it can't track a moving target. And its built-in mic will pick up the noise of the focus motors. If you want to hook it up to a cinema-style manual follow-focus rig, and add a bunch of audio gear, it'll shoot gorgeous pro-quality video at up to 1920x1080 23.976p. On its own, it's inferior to any \$200 camcorder for casual home video.
I haven't found any.
If the D7000 appeals to you, take the time to look up these alternatives before you buy. Prices are roughly what I see them going for in CAD or USD at the major stores as of late 2011.
Nikon's D5100 (\$750) uses the same sensor, as far as I can tell, but is smaller, lighter, a bit cheaper, and has a less sophisticated focus system. It also lacks the U1 and U2 modes, the nice manual override controls, the weather sealing and the built-in AF motor (for AF-D and older AF lenses) of the D7000, and its viewfinder is dimmer and smaller. The photos it makes look exactly the same, but it's a little less pro-friendly.
Nikon's D300S (\$1500) should have been discontinued when the D7000 replaced it. I have no idea why it's still around, especially at a 40-50% price premium over the D7000.
Nikon's D700 (\$2500) is similar to the D7000 in most respects except the sensor (the D700's is full frame, about twice the active area), the AF sensors (the D700 has a few more), the storage (1 CF card versus 2 SD cards) and a few control details. It's heavier and has a much nicer viewfinder, the viewfinder being the main reason why full-time shooters gladly fork over the extra $1500.
Pentax's K5 (\$1100) is competitive with the D7000 in most respects. It might have a harder time locking focus, but is faster to fire once it does.
Canon's EOS 60D (\$1050) is priced to take on the D7000 and, while it seems to be a bit poorer in low light, is generally comparable. It adds a nifty flip-out screen. I think the ergonomics are somewhat inferior to the Nikon.
Canon's EOS 7D (\$1500) is generally similar to the D7000, perhaps a bit faster to focus and some reports say it has less shutter lag. It's AF system is superior, on paper, and image quality is either a touch better or a touch worse, depending who you ask.
Sony's Alpha 55 (\$750) uses a beamsplitter in place of the usual flip mirror, so its AF sensors work in video mode, unlike most DSLRs. But I don't much care for the ergonomics of the no-optical-viewfinder A55, some reviewers aren't thrilled with its picture quality, and Sony- unlike Canon, Pentax and Nikon- has no qualms about selling mediocre optics, or pissing off their customers for no good reason.
As the title says, this is a quick review. Why would I spend my time rewriting that which others have covered in far more detail? If you want more, look here.
Nikon D7000 Review by Ken Rockwell - this is the one that tipped my decision in favour of the Nikon over the Canons
A good photographer can get good photos with just about any functional camera. A bad photographer will always get bad photos. Buying a new camera won't change that; I'd have happily stuck with my 2003 Olympus C750 had its autofocus, settings memory and power zoom not started dying. Any sample photos I post would be reflective of my style and technique, not the camera, so I simply don't post any. Go to a camera store and try the D7000 for yourself if you think it might suit you; you'll learn far more from five minutes playing with the thing than you will from looking at it online.