I’ve just hooked up the LifeCam Cinema to my desktop, and thought an SD comparison was in order. In a stroke of genius, I attached the LifeCam to the top of my Mac so it and my iSight were pretty much aligned — though not so much that it’s seamless. I did a little video so you can compare color, fidelity, and all that. Best to watch it in HD so you can see the differences between the two.
It’s a bit difficult to get a read on detail since I can’t directly overlay the two images — but have a look at these two full-size images from the videos (click to embiggen):
I think the LifeCam has the iSight beat handily in all areas, though neither one is very good at catching motion naturally and dynamic range is pretty much non-existent. Of course, the iSight is a built-in thing the size of my pinky fingernail, and the LifeCam is actually the size of the original cylindrical iSight.
The LifeCam has a better low end in the audio but also has a hiss that gets pretty pronounced if you need to boost the volume. That can be taken out with a mild low pass filter, though.
Full review will be coming a little later in the week.
[Updated: I think this thing is called the Cinema now, not the HD. I'm not by the box so I can't tell. Also, it doesn't appear to work on Macs natively, although some programs are able to at least get a signal from it.]