Death certificates are a good source of information, but sometimes can be inaccurate. It is best to compare multiple documents for accurate information but they are a great starting source to help you know where to look. I have been able to find birth certificate, parents and other documents because a death certificate helped point me in the right direction.
Much information on a death certificate is given by the living. I have one certificate that states: Education: Some college, no degree. I know with 100% certainty that the deceased did not graduate from high school, did not obtain a GED and most certainly did not go to college. Years from now, there is a good chance someone will think that this person when to college.
Causes of death are not always very specific either. This is when it is great to have stories and information from other family members. I have one person who was a miner and died at a young age due to "necrosis". It makes sense that he died of Black Lung. And then there is "cancer". It is especially important for knowing your own direct ancestor's type of cancer. Only recently did I learn my great grandfather died specifically of colon cancer. I have had other relatives have colon cancer as well. Knowing about my great grandfather will help me be on the look out for signs of this disease.
Death is not always a fun thing to discuss, but it is a part of life. Something that cuts us off from information, but death certificates can help us find information too.