According to this New York Times article, neither of the presidential candidates, nor the VP candidates, have been forthcoming enough about their health.
Doctor and journalist Lawrence K. Altman, M.D., is most concerned about McCain's health. He has a history of melanoma, an especially unpredictable form of cancer that can be deadly if spreads to other areas of the body. Even when it is not fatal, treatments "can be debilitating and impair an individual's physical and mental stamina."
Meanwhile, Biden had two brain aneurysms in 1988 and we do not know if he has had any brain scans during the past 20 years. Obama's one-page medical report was almost laughable in contrast to McCain's 1000-plus-page report, but his struggle to quit smoking is no laughing matter. And Palin refuses to provide any information about her health.
I suppose I can see why the candidates would want to be protective of their medical records. In this political climate, even the smallest concern could (and most likely would) be blown out of proportion and used against them. That said, I agree that voters should know more. We need to know what the risks are. A candidate's health is not central to our choices, but it is relevant.