When you start getting into SLR cameras like the CanonRebel XT you are entering a whole other realm. They aren't point and shoot. They aren't light (Ok the rebel is REALLY light for a SLR). They come stock with a lens that competes with a P&S but the camera can be oh, so much more, with other lenses.
SLR's can shoot in RAW which frees you of jpegs. they can be put in manual mode so you can play with any focal length, apperature, iso setting you like. They can be put into manual focus. They give you complete freedom but it comes at a price. they are expensive, large (on purpose, large cameras bodies balance long lenses and are actually easier to hold for extended shoots), and have a learning curve.
If you feel like you want to learn photography, real photography such as composition, technique, ect a low end SLR such as a Rebel is a great place to start. If you just want a light camera to take shots of vacations with once or twice a year, stick with a fully automatic P&S.
