The Canon S3 IS is a wonderful camera, but it is NOT small -- you are going to be lugging it around the parks.
I have two cameras, a digital SLR that is huge, and I take with me for "going out to take photos" hours at the parks without any rides involved, and a smaller point and shoot that goes in my pocket all the time.
The best camera for WDW overall is a smaller point and shoot that will fit in your pocket or knick-knack bag and which still takes sharp photos.
I think this question really boils down to, are you looking for the best camera you can get that you can ALSO take along to WDW and size and weight don't matter...or are you looking for a small camera that takes great photos that is as convenient and small as possible but which will also last you awhile and take good photos in general long after your return.
My own thoughts -- The Canon S3 IS is a great camera - it is as cumbersome as taking a digital SLR with you, but it does take wonderful photos if you don't mind lugging it around. It is currently the top of the line Canon prosumer, now that they discontinued the Pro 1
If you want similar photo quality and size, with the image stabilization built in, then look at the Canon powershot s700 IS -- great shots and image stabilization (i.e. you can take photos while bouncing around on the train or the boat to Downtown Disney and they will still be in focus). It does NOT stop blur if your subject moves. It stops blur if YOU move.
Nikon has a whole series of wonderful point and shoots - Look at their newest line like the P3 or the P4, both of which have Vibration Reduction (their term for image stabilization).
THen there is the middle of the road compact line -- the larger Olympus cameras, and my personal favorite the Canon s80 -- an amazingly compact camera with 8.1 megapixels and an option dial that allows you to set your settings like using a prosumer or digital SLR yet in a small compact package.
My own package -- I use a Nikon D200 digital SLR, but the camera that is always in my pocket while at the parks is the Canon s80 (which replaced my older Canon s50)
Before you buy, decide on what you want in a digital camera overall. Then decide what size camera you are willing to schlepp along with you into the parks, who will hold them if you go on rides (if they don't fit in your pockets) and the like. Then decide on what camera you want.
I would suggest going to your local camera store and playing with differerent sizes and different shapes, look at the features, and decide what fits you the best. WHile this will sound odd, I will add: DO NOT LISTEN TO THE SALESPERSON. YOU decide which features and which camera you want. DO NOT let them sell you something else just cause they think it is "cool."
