Recovery is important, without it your muscles are fatigued and don't function optimally which effects your performance in the gym. A 2006 Journal of Nutrition study found that when arginine was combined with glutamine'"specifically 6.6 - 7.2 grams of this combination daily for 30 days'"training efficiency was improved because muscle integrity and the oxygen capacity of blood carried to the muscle increased.
But it also:
Prevents heart disease. As you already know, l-arginine helps make nitric oxide (NO) in the body, which is one of the reasons that it is able to help with muscle recovery as it increases blood flow. This action also helps keep your circulatory system healthy as it reduces blood vessel stiffness and improves blood vessel functioning, as shown by a French study in the June 2007 issue of the Journal of Nutrition.
Improves performance in the bedroom. This is where nitric oxide really comes into (er'