There are few differences in the Canon "SD" series of cameras.
They may differ in:
Price
Wide Angle/Normal Angle lens
Have or Have Not a Viewfinder
LCD display size
Have or Have Not HD video capabilities

Here is a comparison:

http://www.dpreview.com/reviews/compare_post.asp?method=sidebyside&cameras=canon_sd780is%2Ccanon_sd1100is%2Ccanon_sd1200is%2Ccanon_sd1300is%2Ccanon_sd1400is&show=all

I added the two newest cameras SD1300 and SD1400
They are not in stores yet.

That GE camera they got as a gift:
It should have a 1 year warranty by GE.
Consider taking advantage of the warranty.

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