"I think noise at low light levels means the camera firmware is being allowed to "push" the low light sensitivity past what the CCD can realistically deliver well."

That is true but also manufacturers also decide whether they are going to capture the image with noise or process the image in the camera for noise reduction. Some do and some don't. Typically, you are most concerned about noise during poor lighting conditions with action (movement of the subject). You can post process the images with noise reduction software that works well (much better than in camara noise processing) but it does reduce the detail some. I have never been as concerned about noise levels in action shots beause typically the action transcends the noise.