The 300D sounds fine for what you do. I leave mine in "P" mode (auto exposure) most of the time. It's basically a point and shoot mode, except you can change things like the ISO speed and exposure compensation. In full auto dummy mode (green square icon) the camera decides everything, including whether to pop up the flash... you'll probably stay in this mode for about 30 seconds before it pisses you off enough to switch to "P"
