The one area build quality is a little off the mark is the lens that you can get bundled with the 7D. The Canon EF-S 18-135 lens was announced at the same time as 7D, but doesn't feel like it matches the body for build-quality
It's made from all plastic, for a start, and unlike more expensive lenses doesn't have full-time manual focusing, so you can't simply grab the focus ring if you don't like what it's trying to do by itself
Its specifications are nothing exciting, with a maximum aperture of f/3.5 at wide angle and f/5.6 zoomed in. On the plus side, it's a good starter lens if you're getting the 7D for video – it has image stabilisation, which greatly reduces frame shake when you're zoomed in
Unfortunately its good video credentials are sullied by the fact that it isn't a USM (Ultra Sonic Motor) lens, and so makes all kinds of whining noises while hunting for focus. You only save £160 if you opt for the 7D without the lens, but once you start spending more money on more advanced lenses you're unlikely to look back.
The lack of a full-frame sensor naturally means that the 5D MKII beats the 7D in a straight image quality comparison – but only just. Compared with shots taken by an original 5D, the 7D's 3200 ISO images were noisier, but not to the point of destruction.
The difference between the 5D MKII and the 7D comes when you compare the maximum ISO – the 7D will go as high as 12,800 if you tinker with the custom settings. The 5D MKII goes twice as far, to 25,600
Otherwise it almost goes without saying – the 7D's image quality is almost beyond reproach, and its chief limiting factor will be your abilities as a photographer and the lens you partner with the body.