I've taken most of the Nitric supplements, except for NOXplode. That's the only one.
However, I've taken NaNOX9, Nano Vapor, as well as Black Powder... and in that order, you'll find it from weakest to strongest: NOXplode, NaNOX9, Nano Vapor, Black Powder (my favorite!). It dialates your blood vessels to enhance blood flow to the muscles that you're working. It's good to stack this with multivitamins and/or creatine, but in no way shape or form should you use any type of fat burner supplement with this. For that matter, straight out AVOID stimulants, as that will lead to a bad/unnatural heart rate which could cause several other problems (1 can of Monster + Black Powder = possible cardiac arrest).
You can get some GREAT pumps out of this...but you have to use it in a cyclic rate, i.e.: stacking for a certain amount of time (weeks) and resting (week, end of cycle). This isn't something where if you're just starting lifting you go ahead and pick up and use, it's something for when you plateau. Don't use this for aerobic exercise, you'll only get sick/nauseous (running, swimming, football, etc).
I noticed a significant increase in muscle endurance and strength using nitric supplements than I did without, and that'll happen way more frequently if you don't start out lifting naturally (no supplements, just a good diet, protein shakes and a multivitamin). I'd say after a month or two of lifting naturally, go ahead and start stacking; but don't go straight for all these "high end" supplements. Keep it simple, keep it hard. The harder, the better gains you get (provided you don't overtrain or injure yourself).