Updates seem to come thick and fast where cameras such as this, the Canon S3IS are concerned 
and in this case, the S3 features some minor tweaks in terms of overall changes, but tweaks, which, nevertheless, make a significant difference in terms of what the camera, can produce.
Key to the changes must be the new 6MP sensor (up from 5MP on the S2) and larger, 2-inch colour screen. Other neat kit that beefs up the S3 spec’ includes a couple of new scene modes (more on these in a moment), a new widescreen shooting mode and the addition of a sports mode for high frame rate capture of fast moving action. So, modest changes, but enough to whet the apatite of those looking to purchase an ultra-zoom digital camera packed with neat shooting controls.
And the S3 has these in abundance, from the AiAF (intelligent) focusing system, backed up by a Flexizone AF/AE system that allows you to move the AF point anywhere within the frame with the metering locked to it; ideal for macro or portrait work. Canon Powershot S3IS digital camera review in 6 Megapixel cameras - Pocket-lint.co.uk