Cocoa butter is the natural fat extracted from the cocoa bean. This fat contains saturated fatty acids which lead to a naturally rare high melting point.
Popular beliefs dictate that saturated fatty acids are not optimal for us, they badly affect cholesterol levels and affect our blood vessels.
Having said that, studies are showing that plant-based saturated fats (like cocoa butter) reduce risk of heart disease, whilst polyphenols present in cocoa butter reduce inflammatory processes which are precursors to atherosclerosis. Additional research give evidence for cocoa butter's support of the immune system, and specifically autoimmune diseases such as chronic fatigue.
In my cooking cocoa butter plays a minor role as it is slightly harder to digest due to its melting point. On the other hand, a high melting point improves the shelf life of the products as it prevents breakdown on fatty acids (to harmful bi-products). Therefore, as for everything - I use it in a balanced manner (although I anticipate using it more in future).