Summary: I owned the SD10 for 4 years. It takes nice pictures (notably not THE best) and is easy to use, but the best feature was always the size. It's so compact - perfect for a guy like me that wants to shove his camera into a pocket. It was smaller than even my cell phone. So, when it was time to upgrade, the SD40 was the natural choice. I love the new features and updates that the SD40 offers.
Summary: What a neat little camera. I bought it only a month ago, so far so good. I turned it on and began taking pictures immediately. I hate reading instructions and this camera was very user friendly and very compact. I got it for my wife for Valentines day and she adores the color too. I guess the only negative thing I would have to say so far is that the memory card it came with was very small 16mb. I can not take videos for long or save many pics.
Summary: Features galore. This little thing is great for taking pics in all conditions. My only "complaint" is battery life is diminished in exteme cold (less than 20F). But my skiing pics/videos are awesome.
Summary: A great point and shoot camera! Literally pick it up and begin to take beautiful pictures quickly and efficiently! It's small size lets you throw it in your pocket and head out the door, and it's quick processing ensures nobody gets bored. The SD40 even has advanced settings to fool around with such as manual ISO adjustment and color accent for more creative users. My girlfriend loved this gift!
Summary: PROS: Small; user friendly; takes excellent outdoor pictures. CONS: Limited zoom; flash in low light conditions washes out colors. The Canon SD40 is small, sleek, and takes excellent pictures when it's sunny out. I'm especially pleased with the super-simple slider that lets me switch between picture-taking, video-capturing, and viewing modes. This camera is a winner!