The I-10's overall performance is actually pretty good for such a cheap camera. It can start up and take a picture in just under three seconds, and shuts down again in under two seconds. In single-shot mode its shot-to-shot time is approximately three seconds, which isn't bad for the price, but it pauses every four shots to empty the image buffer. The continuous mode is a bit odd; it shoots pairs of shots about one and a half seconds apart, but then pauses for about four seconds before shooting another pair, which averages out at about three and a half seconds per shot, slower than shooting in single shot mode.
The autofocus system is surprisingly good, focusing quickly and accurately in most lighting conditions even at full zoom. Face detection is very good, detecting even near profile views, but the tracking AF isn't particularly good. I tried tracking on passing boats at the beach and it wouldn't follow any of them, although it was plenty fast enough to get sharp pictures anyway.
The image stabilisation system is also better than one might expect from a cheap camera, providing around three stops of extra stability.
Unfortunately what was looking like a cool and stylish budget camera is utterly ruined by its awful image quality. I've always liked Pentax cameras, and indeed own a few myself, but I wouldn't buy this one under any circumstances. The main problem seems to be the lens, which is worrying since this same lens appears on several other Pentax models. Images are soft and blurry, especially at the edges of the frame, contrast and detail are severely lacking, and even in the high-saturation Flowers scene mode colours are pale and lack saturation.
An even worse problem is image noise, or rather the massively heavy-handed noise reduction system. Its effects are visible even at 100 ISO, and it starts blurring out finer detail at 200 ISO. At 400 ISO picture look like they were shot through a frosted glass window, and it just gets worse from there. Shots at 1600 ISO are effectively unusable, and the 3200 and 6400 ISO settings, available at 5MP resolution only, are completely pointless. This is very disappointing; I like the I-10's bold styling, and it is a nice camera to use, but with such poor image quality it's impossible to recommend it.
The Pentax Optio I-10 is a disappointing camera from a company that really needs a successful compact or two right now. Build quality is average at best, and the quirky retro styling doesn't disguise the lack of features. Handling is fairly good, low light focusing is excellent and performance isn't bad either, but it is ruined by very inferior image quality, especially the terrible noise reduction system.