Conclusion - Pros
Incredibly compact design
Slim enough for any pocket or purse
Beautifully built and all-metal construction
Excellent color
Manual (custom) white balance
Very good resolution
Good exposure and generally very reliable focus
Good flash performance at short distances
Very, very fast
Good screen
Excellent movie mode
Nice handling and easy to use interface
AF illuminator
Excellent macro mode
Conclusion - Cons
Strong purple fringing
Some edge softness at wide angle/max aperture
Battery life when using LCD not fantastic
Occasional lens flare
No exposure information in record or playback mode
Very little manual control
Overall conclusion
In an ideal world buying an ultra compact camera would not involve any compromise at all. But this ain't a perfect world, and if you want a camera you really can carry with you anytime, anywhere then you have to accept there will be some trade-off in terms of absolute image quality. The SD300 is, fortunately, more than just a slim, cool, stylish camera with enough silly names (ELPH, IXY, IXUS) for an entire episode of Monty Python. It's a fast, easy to use, well-specified camera that can genuinely claim to be pocket-sized, and it produces images that - whist by no means perfect - are sharp, clean and colorful, and it does so with the minimum fuss. It's so small, and is so enjoyable to handle and use that you cannot help but take it with you wherever you go, something you might hesitate to do with a larger camera.
The new lens Canon designed for the SD300 (and little brother the SD200) seems more than able to deliver the level of fine detail a 4MP chip demands, but the sharpness does fall off a little towards the edges and corners, especially at the wide end of the zoom and F2.8 or when shooting close-ups, and there is a small amount of visible vignetting. But I found little to complain about when printing the images, and the simple truth is where it matters to the target market; exposure, color, focus, speed and noise, the SD300 exceeds expectations. If you can live without manual control over exposure (or any indication of shutter speeds or apertures) this is the perfect pocket camera and an ideal alternative for the days you don't want to take a bigger camera out with you. If it hadn't been for the lack of shutter speed information and the problems with edge sharpness and fringing, this would have been a Highly Recommended, as it is I wouldn't hesitate to recommend it to anyone wanting a small, fast, capable camera.