You have to wonder why Canon has smooshed three almost identical cameras into this part of the market: http://www.usa.canon.com/consumer/co...modelid9=14901
In comparing Alpinord's SD1000 to my SD800 IS (naturally I wanted to see what other toys were out there) I identified really only three differences between his and my models:
The 800 has a focal length span of 28-105 whereas the 1000 has 35-105.
The 800 has image stabilization which I've turned on and off and am not sure it offers anything, but it's nice to have the choice.
The 800 has a slightly faster shutter, 1/1600 sec vs. 1/1500, but really that's splitting hairs.
The 1000 weighs .9 oz less.
The biggest difference in my mind is the optical zooms: 1000 has a 3x zoom, and the 800 IS has 3.8x.
Beyond that? Practically an identical camera.
The 850 IS has more pixels than either the 800 IS or the 1000, but with these lenses, does that really buy you anything? I'm not sure. Its zoom is the best of the three at 4x. That alone might make me get the 850 IS if I were buying today.
I checked Amazon and the price differences among the three are pretty noticeable:
1000 - $208
800 IS - $292
850 IS - $347
Here's another feature comparison I found on Amazon: http://www.amazon.com/gp/comparison/...000NK8EWI&bf=0