Keep in mind that I have never tried these supplements,
From the site: http://www.musclesurf.com/what--is-nitric-oxide.html
What Is Nitric Oxide?
Nitric oxide (also known as "NO") is a gas that functions as a signaling molecule (neurotransmitter) telling your body to make blood vessels relax and widen.
What Does Nitric Oxide Do?
NO gives more blood to organs when needed. When your arms need more blood supply for movement or for warmth, for example, the brain signals the blood vessels in the arms to release NO.
After a big meal, NO sends more blood to your stomach to help you digest the food. It controls blood pressure, giving more blood when you exercise, and reducing the flow of blood when our body is at rest.
NO is also responsible for the relaxation of blood vessels in the penis, causing the blood to pool which produces an erection. The anti-impotence drugs Viagra ® and Levitra ® work in much the same way.
Nitroglycerin works to help chest pain by releasing NO gas, which dilates the blood vessels in the heart.
What is Nitric Oxide Used For?
Bodybuilders and athletes know that Nitric Oxide is a valuable part of their success because it’s responsible for blood flow, oxygen delivery, glucose uptake, muscle velocity, power output, and muscle growth.
Increasing Nitric Oxide levels can deliver continuous muscle-enhancing benefits like:
Faster gains in lean mass
Providing better muscle recovery
When you exercise hard, Nitric oxide opens the blood floodgates, allowing blood to surge in. This is the "pump" so coveted by bodybuilders and athletes alike. But exercise-induced pumps are only temporary. They disappear soon after exercise has ended.
But new and effective NO stimulator formulations are changing that. The muscle pump you get from these supplements can help you retain that post-exercise, blood-engorged, rock-hard condition longer than before. Even massive, vein-popping pumps show no sign of diminishing. That's because NO generates a continuous surge of blood that courses through the skeletal muscle throughout the day. So muscles remain engorged and steel-like all day long.
Maybe someone who's tried it can tell you have effective it is.