The larger LCD on the XSi necessitated a change of layout for the controls on the back from that of the XTi. Overall, I think I like it better than the older design with Menu, Disp, Review, Jump, and Delete buttons down the left side.
Like Nikon, Canon ships the XSi with an optically stabilized update of its 18-55mm kit lens. Although optical stabilization lets you preview the stabilized results, sensor-shift stabilization allows for cheaper comparable lenses in the long run.
Of course, if accurate color isn't your thing, you can play with Canon's Picture Styles and tweak reality. Frankly, I think you're always better off shooting the most accurate color possible--you can always pump it up later, but you can never recreate reality from a tweaked original. That's why I tend to discount features like this.
You can bring up the exposure on the XSi's photos without inflicting excessive noise on them. The flash didn't fire for this shot of Kendra, but I was able to fix the exposure suitably for Web use. I don't think I'll be printing it at 13x19, though.