Canon basically ceded the entry-level pro performance market to Nikon in 2005 with the arrival of the D200; since then, Canon's 30D, 40D, and 50D have taken the slower but less-expensive road, with a relatively stagnant AF system, that Nikon leapfrogged. But with entirely new AF and metering systems, a new high-resolution eight-channel readout sensor coupled with dual Digic 4 image processors and a new 100 percent coverage viewfinder, plus 1080p video capture, the 7D looks like an aggressive attempt to make a comeback.
In addition to a body-only version, Canon sells the 7D in a kit with the 28-135mm f3.5-5.6 IS lens (44.8-216mm equivalent). I'm not really fond of it, though, and if you're looking for a starter kit, I'd recommend the newer 15-85mm f3.6-5.6 IS USM lens (28.8-136mm equivalent) instead. It's a lot more expensive and a bit shorter, but I think it's a significantly better lens.
One of the heavier single-grip dSLRs available, there are no radical design departures in the 7D but there are tons of subtle, and a few conspicuous, interface changes that greatly enhance the fluidity of the camera's operation. The new viewfinder is great, comparable with that of the D300s: big and bright, with an optional overlay grid. It's also slightly more comfortable than the D300s' because of the larger eyecup. (Since I didn't get to take the camera to Antarctica to test its weather sealing, cold resistance and ruggedness, I'd follow Ole Jørgen Lioden's testing on that, if you're interested.)
Adding to its traditional array of buttons for metering, white balance, autofocus, drive mode, ISO sensitivity, and flash compensation the 7D now includes an M-Fn button used to cycle through the AF point options, plus Canon brings the LCD illumination button into action for registering the orientation-linked AF points. Unfortunately, the buttons are very difficult to differentiate by feel, and the M-Fn and illumination buttons are even smaller and harder to use than the others. Following trends in consumer dSLR design, the 7D now also has an interactive control panel for changing frequently accessed settings, called up with the Q button. Though I generally prefer buttons and switches for quick access, the control panel is ultimately easier to use than trying to differentiate between the small buttons on the top of the camera without looking.
Canon consolidated the screen for programming the behavior of the buttons and dials with a visual guide as to where they reside on the body. It's a very nice design.
By adding a specific switch with start/stop button for Live View and Movie capture modes, Canon removed a lot of the operational ambiguity of the 5D Mark II (where you have to have a custom setting enabled just to trigger Live View, for example), and allows the Playback button to function normally, unlike the D300s. It definitely adds to the usability of these modes. More subtle enhancements include an updated switch for the thumbwheel lock and the odd addition of a silver ring on the thumbwheel. The joystick remains unchanged, but I think its design could've stood some tweaking; it's still a bit too easy to accidentally push up when you're trying to go left or right.
By adding a specific switch with start/stop button for Live View and Movie capture modes, Canon removed a lot of the operational ambiguity of the 5D Mark II (where you have to have a custom setting enabled just to trigger Live View, for example), and allows the Playback button to function normally, unlike the D300s. It definitely adds to the usability of these modes. More subtle enhancements include an updated switch for the thumbwheel lock and the odd addition of a silver ring on the thumbwheel. The joystick remains unchanged, but I think its design could've stood some tweaking; it's still a bit too easy to accidentally push up when you're trying to go left or right.