Casio compacts usually have excellent overall performance, but the Z1 is surprisingly slow. It takes just under three seconds to start up, and well over two seconds to shut down again, which may not sound too bad, but it's about twice as long as the EX-Z85. In single-shot mode the Z1 has a shot-to-shot time of just over three seconds, which again is slower than normal, however in continuous shooting mode it can manage approximately one shot per second, with a faster burst of up to four shots at approximately 1.5fps.
Part of the problem is the autofocus system, which is much slower than Casio's normally ultra-fast focusing. It also performs very poorly in low light, which again is unusual for a Casio. The Z1 has no AF assist lamp, so it can't focus at all once light falls below a certain level. Unfortunately that level is still bright enough to read by.
There is a possible explanation for this apparent inconsistency. It's a fairly common practice in the digital camera industry for branded products to be manufactured in huge Chinese factories owned by other companies, albeit to the brand company's specification. Casio has been known to do this, so maybe the Z1 is actually made by a different manufacturer to the other recent models. This is mere speculation on my part, but it would explain why the Z1 doesn't look, feel or perform like any other Casio compact.
One thing the Z1 does get right is its overall picture quality. Admittedly it's not utterly brilliant, but it's far better than average for a low-cost ultra-compact. A lot of the credit goes to the lens, which provides excellent corner-to-corner sharpness, and although it does produce quite significant barrel distortion at wide angle, it is pretty much free from chromatic aberration. Exposure is accurate, colour reproduction is excellent, however the very small 1/2.3-inch sensor doesn't have a lot of dynamic range. Images also have a slightly over-sharpened look to them which does have an impact on the level of fine detail. I've seen better from other 10MP compacts, including previous Casio models.
The main IQ problem area is image noise. Picture quality at 64 ISO is very good, with clean smooth tones, plenty of detail and no visible noise, but this doesn't last long. By 200 ISO there is visible noise in the darker areas, although the noise reduction preserves the detail. By 400 ISO the noise is a real problem, and the detail is starting to fade. By 800 ISO there are colour artefacts, a large loss of detail and visible noise right across the frame. Naturally 1600 ISO is even worse.
When everyone else is making 12x zoom travel cameras with HD video, the Casio Exilim EX-Z1 is something of a throwback. It's a relatively unsophisticated camera, but it is at least well made and looks good. Unfortunately its poor handling, slow overall performance and lack of low light ability make the Z1 a poor choice for social snapshot photography. There are better cameras for less money, including several from Casio.