i was in the same situation. and i choosed black Sony T30. it is not a choice many people on this forum will make, but it's my choice. reason as follows
Sony T30: Pro: 1. Battery life (420 pictures) 2. Style (the black one is very beautiful!! piano black) 3. optical IS (although i think canon's IS works better, i can still take good pictures down to 1/15) 4. 3inch LCD. the LCD is big and bright. it is reflective type that u can still use it under direct sunlight Con: 1. Battery charge time.. it takes 5 hours to fully charge the battery!! 2. non-standard cable. Sony use one cable for everything (USB, AV....) it is not standard USB cable. 3. MS DUO card. (compare to SD card, not becasue of the price (which i think is about the same now) it is becasue u can buy Sandisk Extreme II Plus with the USB connector)
Canon 850IS Pro: 1. 28mm (this is a good plus when u need it) 2. SD card. as i said above. u can get one with USB connector. this is a BIG plus! u have to try it to know the benifit. 3. Image stabizer works better than T30. i can get good result down to 1/8 sec! 4. the face tracking works very very well. i think this is a feature other menufacturers will try to copy in the future. this make "half press" technique looks stupid. Con: 1. battery life is only 250 pictures 2. bigger and heavier than T30, if size is important to u