1) Has anyone heard of trustedreviews.com? Are they trustworthy?
I see people post links to a review there from time to time. But, I never visit it personally. From my perspective, the reviewer seemed a bit too enthusiastic about the image quality from that Fuji.
I see a lot of corner softness and purple fringing from that lens. Dead Center looks OK (other than a few sharpening artifacts in some of them). But, I think too many compromises were made trying to fit a 3x optical zoom into a body that tiny from what my eyes are telling me.
Each reviewer tends to have a certain style, and unless you've followed a reviewer, it's hard to judge how to interpret their findings. So, I'd let my own eyes be the judge. I also prefer it when I can see the same subjects in similar conditions from multiple cameras (for example, the way Steve tries to include some of the same subjects in most reviews here).
2) The Fuji's have better ISO sensitivity, but don't include optical image stabilization. (Assuming a still subject) Would the higher useable ISO of the Fuji's be better or worse than optical image stabilization used in the other cameras I've mentioned?
That Fuji Z5fd you're looking at uses a smaller sensor compared to the models you thought were too large (F30, F31fd). It's noise levels are not going to be the same. I see pretty aggresive noise reduciton being used in those sample images. The appearance of noise is kept under control in light that good (and low light is the best way to see how one is going to perform).
But, even in lighting that good, I see loss of detail, decreased saturation and more. I would not expect to use that camera at it's highest ISO speeds and be satisfied with it (especially since it's probably going to be a lot worse in poor light where you'd need the higher ISO speeds).
I realize that this is comparing general technologies, so if you'd prefer to compare specific models, how about comparing the OIS of the Canon SD800 IS to the high ISO of the Fuji F31fd.
It depends on what you want to shoot and the conditions you're shooting in. It's all a tradeoff, and just because you have higher ISO speeds available doesn't mean you want to use them (since noise will increase with ISO speed).
Between the Z5fd and Canon 800IS, I'd probably go with the Canon. From what I can see looking at the samples, I think the Canon could probably do about as well at higher ISO speeds retaining detail as that Fuji.
Without samples taken in the same conditions with both cameras, it's hard to say for sure. But, I don't think they're very far apart and the Canon has stabilization, better feature set, better flash range, what appears to be a better lens, and more.
As for the F30d/F31fd, if you're primary purpose is taking existing light photos of non-stationary subjects in low light (i.e., people that may not be motionless), it may make a good option in a pinch.
It's probably got about a stop benefit over the other Fuji model (Z5fd) from a noise/detail retention perspective from the little I can see from it (and I'd need to see more samples of both in the same conditions to form a better opinion.
If your subjects are mostly stationary, I'd personally go with the Canon over either one of them. But, if you need to shoot non-stationary subjects in low light often without a flash, the Fuji f30/f31d models may be a better option.
No one feature is going to be best for all conditions. You need to look at the camera as a whole (lens, image processing, usable ISO speeds, and more) to get a better idea of what compromises you'll make for the shooting that you will do more often (and any choice will be a compromise in one area or another).