HOW MUCH DOES SENSOR SIZE MATTER?

I was reading through an article on cambridgeincolour.com, which talked about the factors that the sensor size of your camera would influence. The author shares the research he made when he was contemplating if upgrading to an EOS 5D was worth it. Some of the facts he mentions are obvious, like the effect on depth of field, crop factor and noise, but there seems to be much more than that. There is a more detailed analysis on noise level, influence on dynamic range, diffraction and a few other factors. You may never bother to buy a camera with a smaller or larger sensor than what you have, but still the article is educative and worth reading.