for the average person......no

Depends how much sugar etc. that gets put into it.

caffeine contricts blood vessels in the brain because it mimics adenosine(which slows down cell activity and cause vessels to dilate in the brain), caffeine binds to these adenosine receptor sites so the body is tricked thinking the adenosine is there.. therefore no vessel dilation. this is also why caffeine is a stimulant

blood vessel constriction means big problems for people who already have high blood pressure, heart disease.. ect, because in those cases, the vessels already have a decreased diameter..

one the other hand caffeine also causes adrenaline to be released.. if you want details, just ask !!

probably more than u wanted to know .. haha

It also plays with insulin response, but one cup is usually not considered bad. Most thing are good and bad at the same time for you.