Being a mid-range model, the IXUS 90 IS doesn't have the beautifully rounded design seen on the IXUS 950 IS that we reviewed last summer - that look has been carried over onto the IXUS 970 IS. That said, the IXUS 90 IS still looks very good and has a solid, metallic feel to it when held in the hand. It's not the lightest compact out there - Canon quotes a weight of 155g, but that's without the battery, which is somewhat pointless considering the camera can't be used without the battery inserted. Placing the IXUS 90 IS on the TR scales with the battery and memory card in situ revealed a "working" weight of 180g. Dimensions of 92 x 57 x 21mm (WxHxD) make it pretty small but not as svelte as some competitors. That said, some very small compacts can be fiddly to hold and use, but the IXUS 90 IS is just the right size for comfortable operation.
The trend for ever spiralling megapixel counts continues with the IXUS 90 IS sporting a 10-megapixel CCD. I'm not convinced that squeezing more and more pixels onto such a small sensor is a good idea, as it can't help but introduce more noise into your images. That said, Canon's image processors are legendary, and this IXUS is equipped with the DIGIC III, which does a sterling job of keeping CCD noise in check, even at high ISO settings. Up to 400 ISO there's pretty much no trace of noise at all. The next step to 800 ISO reveals some CCD noise, specifically in darker areas of the image, but on the whole pictures are still usable at this setting. The 1600 ISO setting is best avoided however, with the resulting images looking mottled at best and resembling a dirty mess at worst.
For the most part the Image Stabilisation works very well, and definitely gives you the option of taking pictures in low light without a flash. However, you still need to be sensible when shooting indoors, especially if there's a strong ambient light source like a window. Forcing the flash off and relying on the IS removing camera shake from a longer shutter can result in high intensity areas being whited out completely, whereas using a fill-in flash would have avoided such a problem. Ultimately most users will learn when to use a flash and when to rely on IS through trial and error, but it's definitely good to have the flexibility.
The auto-focusing is staggeringly quick, faster than I've ever seen on a camera this size. Not only does it focus quickly, but it also picks out exactly what you want to focus on the majority of the time. Take a shot of a car head on and the IXUS 90 IS will automatically grab both headlights as focus points, keeping the whole width of the car sharp and clean. The shutter release also lends itself to fast operation, with a very definite half-press to invoke the auto-focus, unlike many cameras that leave you either not pressing hard enough, or pressing too hard and inadvertently taking a blurry shot.