Here’s the MacWorld Buying Advice on Canon Digital Rebel XTi (or 400D): “You need to get your hands on the Digital Rebel XTi before you can make an evaluation as to whether it’s right for you. If you like its size and feel, then you’ll find it to be a full-featured camera that yields excellent image quality at a very reasonable price.

The vibrating cleaning cycle occurs both when you power on and off, but Canon has wisely made the power-on cleaning cycle interruptible. A half-press of the shutter stops the cleaning cycle so you can shoot immediately. Dust is a problem for any SLR, so these changes are valuable.

…The XTi yields excellent image quality, with very little noise up through ISO 400, and minimal noise at ISO 800 through 1,600, the maximum speed available. An increase in resolution can sometimes result in noisy photos, but Canon has managed to increase the resolution on the XTi’s sensor without increasing the noise. As such, the extra two megapixels are welcome, and provide much more output and cropping flexibility.“