I have both the Ixus 850IS and the Fuji F11 (predecessor of F31fd).
Image quality wise, I'm definitely happier with the Fuji for indoor shots. Outdoor shots with good lighting, the 850IS is slightly better in terms of less blown highlights and accurate metering. But both are excellent outdoors.
The Fuji is snappier to use and I find the buttons more user-friendly (The 850IS has a recessed button which is in the centre of the camera - hard to switch on with one hand. Also, you need to turn the mode dial to view the pictures. With the Fuji, you just press a button on the back, and can switch back to shooting mode just by half-pressing the shutter button).
IS is useful, but if you have smooth high ISO, you don't really need IS.
Size wise, I find the 850IS a little too small when shooting, although the feel is very nice when you just carry it around. I prefer shooting the Fuji. Fast, responsive, just the right size for my hands.
So why did I get the 850IS?
Well, it's got 28mm at the wide end. The Fuji doesn't. It's also got a viewfinder (but I must say a pretty lousy one). Most importantly, the F11 officially belongs to my wife, and I needed an excuse to get a new camera.
There's a HI-Auto ISO mode which basically does auto-ISO, except one stop higher for faster shutter speeds. Useful for situations when you don't like to worry about which ISO you're in.
The 850IS is great for video, because of the image stabilization. It takes 640x480 video at 30fps, and the video is very sharp and smooth. And with the wide angle, the video looks very fun and dramatic. Not sure about the Fuji, but you can take continuous video with the 850IS - up to 4GB of video I think. Great stuff.
not familiar with the panasonic so cannot comment on that. but the wide angle on canon applies to all format. (Based on testing on my fren 850IS) If wide format, then some portion along the top edge and the bottom edge will be cropped ( i think).
