I still haven't had the chance to buy a bottle, I'm thinking of NOX2. After my research and talking to a few of my buddies at the gym in the university, they thought the stuff was great. All Nitric oxide products are supposedly just the amino acid Arginine and the enzyme that helps break it down to NO, thus water is essential to keep the Arginine from building up in your kidneys. 2K2GT, your brain blood vessels are made out a different material than your normal arteries and veins, it does not constrict any brain vessels. Lower blood pressure may speed up your heart rate, but this is only temporary, the NO is actually a secondary messenger in the nervous system and due to the dilation of blood vessels causes an increase in production of red blood cells in the blood stream. Essentially after the NO builds up in your neurons it causes the amount of blood in your body to increase dramatically. This allows more oxygen to reach the tissues of muscles, etc.
The only thing dangerous about this stuff is if you are doing a large amount of cardio (without accentuating with weight training), not eating sufficiently, or not drinking enough water.
Edit: I'm not saying it can't do anything detrimental to you, many neurological diseases affect the human nervous system due to excess specific amino acids. I'm just stating the facts that I've learned in my Human physiology and Neuroscience classes.