I have a Canon SD630. I like it, but I'm thinking about upgrading to something that is going to give me better image quality and some image stabilization. I'd like to stick with the Canon SD series, because I like the form-factor and ease of use. Plus, I already have an extra battery and camera case. These seem to be the most commonly recommended models: SD1100IS SD780IS SD850IS Price is not a really factor, as they are all within my range. Really, my only concern is image quality. - Which one do you all think will give me the best general, overall image quality? - And are any of these going to be significantly different than the SD630 in that regard? - And am I overlooking an SD model that I should be considering? I've read a bunch of reviews, but I can't really tell/decide. Help.