[BRPORSCHE]

I have the XTi with the 18-55 mm IS and I also just bought a 55-250 mm IS lens.

There are two major differences between the XTi and the XSi that you should know about:
1. The XTi does NOT have real time picture oin the LCD screen. You must look through the viewfinder.
2. The XSi takes SD memory, not CF, which is considerably cheaper per gb.

Either way you will be happy with your choice. They are GREAT camera's, and I honestly couldn't go back to a cheap point and shoot. Something you will have to keep in mind is that you are going to want to upgrade bodies. I am craving a T1i baaaaaaaaad.