Im in the market for an upgrade, too. I currently have the SD500 but am not happy with the indoor shots at all (with flash are good, but without are terrible). This seems to be the same line, and I DO like the SD series, the only downside was the poor indoor shots without flash.

So if anyone knows anything about the indoor pics... that would be my determining factor

I was looking into an S2 IS but I wanted something that was easier to carry around and fit in my purse, and the S2 series is a little too bulky for that. Considering I already have the XTi lol