"This camera has features including a 8.0 Megapixel, 1/2.5-inch CCD, DIGIC III Image Processor, 12x optical zoom lens with a shift-type optical Image Stabilizer (IS) system and 2.5-inch vari-angle LCD monitor with wide viewing angle. It uses four AA batteries to shoot up to approx. 170 images (based on the CIPA standard when the LCD monitor is on), and SD memory cards, SDHC memory cards and MultiMediaCards for the recording media. Images are utilized with a direct print compatible printer, computer and TV via USB 2.0 Hi-Speed."
For me, the main upgrade is the hotshoe, and vide long play...what can you say about this upgrade from S3 IS...
more info here
http://web.canon.jp/Imaging/pss5is/index-e.html