When it comes to entry-level point-and-shoots, Canon's A-series PowerShots consistently excel in picture quality. That certainly holds true for the 16-megapixel A2400 IS and A2300.
The two simple sub-$150 ultracompact cameras are good choices for anyone whose needs don't extend far beyond the occasional fully automatic snapshot of patient subjects taken in daylight. I say that because the cameras perform fairly slowly and their photos get noticeably softer above ISO 200.
I reviewed the A2400 IS, but the only difference between the two models is optical image stabilization; the A2400 IS has it, the A2300 does not. For the $10 price difference between them, spend the extra money for the A2400 IS -- especially if you'll be doing any indoor shooting with the camera.
If low-light photos without the need for a flash or tripod are important to you, consider saving up a bit more money and getting the PowerShot Elph 110 HS, which is actually a better camera all the way around.
As with most compact cameras, the A2400 IS' photo quality noticeably drops off at higher ISOs, so getting the best pictures really depends on how much light you have -- the more, the better. Fine detail and sharpness are very good up to ISO 200 (though a little sharpening with photo-editing software improves things). Photos get noticeably softer at ISO 400 due to heavier noise reduction.
Pixel peepers will see the image noise and artifacts at all ISO sensitivities, but it's really not visible at reduced sizes until you get to ISO 800. As long as you don't mind increased softness and noise -- including faint yellow blotching -- ISO 800 is usable for small prints and Web sharing. The camera's highest full-resolution sensitivity is ISO 1600 and I'd stay clear of it unless you really need to take a low-light photo.
On the other hand, because of consistent color at higher ISOs, the photos are better than those of other cameras at this price; they just get slightly washed out at and above ISO 400. In fact, color performance overall is excellent from the A2400 IS -- bright, vivid, and accurate.
Something to keep in mind, too, is that although the camera's lens starts at a bright f2.8 aperture, it shrinks to f6.9 with the lens zoomed in. That means when you go to use the full zoom, you're going to need a lot of light or a high ISO sensitivity to keep the shutter speed fast enough to prevent blur from motion or hand shake. (Another good reason to skip the A2300.)
Video quality is good enough for Web use, but nothing spectacular. Panning the camera will create judder that's typical of the video from many compact cameras, and you'll notice motion trailing on fast-moving subjects. The zoom lens does not function while recording, but you do have a digital zoom; I suggest not using it, as the results are not pleasant.
Shooting performance is OK; not fast enough for regularly photographing kids and pets, but not so slow that you'll get frustrated. From off to first shot takes about 2.4 seconds. The wait between subsequent shots averaged 2.8 seconds for us; using the flash bumped it up to nearly 4 seconds. Shutter lag -- the time from pressing the shutter release to capturing a photo without prefocusing -- is 0.4 second in bright lighting and 0.7 second in low-light conditions.