When you reach the point in your photo journey where you'd like to grow and experiment, then it's time to get a camera system that grows with you. That's the beauty of DSLR cameras. And entry level rigs like the Canon XSi can be used on full auto, but also have full manual, shutter priority and aperture priority modes. So, you can venture out into experimenting with various features as you're comfortable doing so.

DSLRs also give you better options. Point and shoots are for snapshots. Flashes that are only good for about 9 feet, shutter lag, and small CCD chips which have been stuffed with enough megapixels that noise becomes an issue in low light. Fine for a shutterbug, but for someone who takes photography a little more seriously than capturing "kodak moments" definitely you're ready for the next level.

But remember this. You're looking at a system here, not just a camera body. Bodies will come and go, but your lenses will move from body to body. And since you can still get the XT or the XTi, I would save money there and invest the rest of the money on a good zoom lens that will serve you well. Then, when prices drop next year on the XSi, you can consider selling that older body on eBay and upgrade to the XSi.