I got up an hour earlier today so that I could slowly wander the 3/4 mile from my Light Rail stop to work and take photos along the way with my brand-new Canon XSi.
Although I had my other two lenses with me, I stuck with the new kit lens, an 18-55mm EF-S IS (image-stablized) lens, in order to see how it performs.
I was very pleased with both the camera and lens; no doubt, some of this was due to the New Toy Effect. But several things jumped out at me:
First and foremost, compared to my old "original" 2003 Digital Rebel (D300), the camera comes to life instantly. The D300 took 2-1/2 seconds to "wake up." That is, when you first turned it on, it would take that long to be ready to shoot. Also, whenever it went to sleep to save power, usually after a minute or two of inactivity, it would again take 2-1/2 seconds to wake up. The XSi, on the other hand, comes alive instantly, both from a cold start and after a period of inactivity. All it takes is a half-press of the shutter button.
I've missed quite a few good shots, especially doing event photography, with the D300 because of the wake-up time. Now, it turns out this isn't something you need to buy the XSi for - each model subsequent to the D300 has had this: the XT, XTi, and now the XSi. It's a function of the improved image processing electronics since the D300.
On the other hand, one thing that is new to the XSi is Auto ISO. This means that I can walk around and the camera figures out, from the lighting conditions, shooting mode, and other factors, where to set the ISO "film speed." Before, I would usually set it at 400 and leave it there; for the sunny morning today, the XSi set it for me at 200. If I had continued taking photos indoors, it would probably have bumped it up for me as necessary. Very cool! This feature is something Nikon has had for a while, and it's about time Canon adopted it (I believed it first showed up in Canon's 40D.)