I take a lot of pictures, and I've found that one of the keys to getting the photos you really want is simple: have a camera handy. Rarely do I go anywhere without one, and so a nice hike along the river gave me the excuse I needed to get to know the 40D a little better.

I can see key settings through the viewfinder, like my shutter speed, how many shots I can take in burst mode before the buffer fills up, my aperture and exposure settings, and the sensitivity or ISO setting.

Why it's nice to see the ISO setting through the viewfinder
"ISO" refers to the camera sensor's sensitivity to light. A high sensitivity setting lets me capture images in low light, while a low sensitivity setting is best for brightly lit environments. I really liked having the ISO setting visible through the 40D's viewfinder. Otherwise, I may be shooting inside in low light using a high sensitivity setting, and then waste a bunch of shots outside the next day because I forgot to turn it back down for outdoor lighting, resulting in "blown out," overexposed photos.

Image sensor cleaner
Dust can collect on an image sensor whenever you remove a lens from your camera, or when you're using a zoom lens that extends and contracts, sucking in air and dust in the process. Over time, dust specks can start to appear in your photos, and cleaning an image sensor by hand is best left to professionals. Having a built-in sensor cleaner is quite handy if you change lenses a lot. You can set the 40D's sensor cleaner to gently shake the sensor free of dust every time you turn the camera on and off, or you can engage the cleaner manually at any time through the menu.

The 40D's screen is big and bright.

Bright 3" LCD screen
A 3" LCD screen dominates the back of the camera, and it's plenty bright enough to see in the sunlight. Colors on the screen are rendered accurately, probably the most important thing to me because I like to peek down now and then to confirm that my shot is exposed properly. I like to turn on the "highlight alert" feature when I'm outside, which lets you know if part of your image is overexposed.

The screen is capable of live view too, kind of like a point-and-shoot camera. I say "kind of" because you lose autofocus in live view, so it doesn't quite function like a point-and-shoot. It's probably most useful in a studio setting, or for close-up macro work.

Capture the action: high-speed shooting
The 40D is very fast. It's rated at 6.5 frames per second in "high-speed burst mode" at faster shutter speeds. When I was outside shooting geese flying around a lake, it was more than adequate. It's definitely a great choice for folks who like taking pictures of sports. You can take full advantage of the 40D's burst mode thanks to an upgraded buffer, or how many shots you can take before the camera has to pause to write files to your memory card. It'll take 17 RAW files or 75 large/fine jpegs before it needs to stop and catch up. A quality memory card with a fast write speed can save the photos faster, freeing up space in the buffer so you can shoot more pictures.

The 40D's high-speed burst is great for shooting wildlife action shots.