I've taken nitros oxide. (Bought one bottle, pill form) I didn't develope any ill effects from it. I noticed it seem to make me appear more lean and give me definition. Veins became a bit more apparent. I was also taking protein powder at the time and working out more regularly(4 times/week) so i can't say how much was from the n02. I believe its suppose to open the blood vessels. So that, taken in addition with creatine, which helps with blood flow also, seem to be a couple of supplements that work well together. I haven't tried creatine as of yet, but my manager at my work took both the creatine and n02 at once, and enjoyed the results, telling me if he was to get serious about lifting again, he'd take both again. I think if your only working out casually though, definately stay away from the supplements, as they might just make you pudgy.