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.
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 18-85mm 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.
By adding a specific switch 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.
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, though I think its design could've stood some tweaking.
Following trends in consumer dSLR design, the 7D now has an interactive control panel for changing frequently accessed settings, called up with the Q button, which is a lot easier than trying to differentiate between the small buttons on the top of the camera (see subsequent slides).
There's also a welcome new Raw/JPEG override button, which overrides the camera's current single-format setting for a shot; in other words, if it's set for Raw or JPEG it will shoot Raw+JPEG for one frame. Because of they way I shoot (Raw+JPEG with the occasional need for just a low-res JPEG), I'd find it a lot more useful if you could do the opposite: program it to override Raw+JPEG as well, with the option to make the setting sticky until canceled.
Canon went from very few AF options to a gazillion in one model. Of course, there's the veteran full automatic AF selection. Spot AF is a sub-area of the traditional single-point AF, and for both of these you can choose from any of the 19 AF points. AF point expansion lets you choose any of the AF points plus the three or four (depending upon location) surrounding it.
Zone AF is similar to AF point expansion in that it allows you define clumps of points in the center, top, bottom or sides of the full AF area, but in contrast to expansion, where you still choose the primary focus point, the camera automatically chooses what to focus on within the defined zone. The bulk of these are really designed to improve focus tracking during burst shooting, and much like Nikon's AF system you have to think very carefully about matching the AF choice with the shooting situation.
Very few users need all of these options, and Canon provides a solid interface for enabling or disabling the choices to minimize on-the-fly confusion. And that M-Fn icon at the top is there to remind you how to cycle through the different zone options--you cycle through the points with the joystick or thumbwheel--which is pretty easy to forget.