To answer #1, I have the S3 IS, and my wife has the S2 IS. We generally shoot using the "M2" setting, which is 1200x1600, and those photos are usually around 300-500 KB. At 500 KB, you could get close to 2000 pictures on a 1 GB card. If by "small format" you mean the 640x480, you could get much more. But the manual does have a chart showing better estimates.