OK guys...I understand where you are coming from, it sounds like a huge scam. I was given two canisters of this stuff by a company rep to try, and I figured the same thing. I brought it to the gym with me on a heavy leg day. I tried it a few different ways, before and after sets and this is what I found:
It didn't do a lot to increase performance when used before a set. AFTER a killer set of squats, however, the kind where you sit down and gasp for air for a minute trying to catch your breath, the canned oxygen was incredible for recovery. I did a couple of sets normally, got winded as usual, and recovered as usual. After that, I did a set, got winded, then took 5 big puffs from the canister of oxygen. My heart rate and breathing returned to normal faster than you can believe. I did it multiple times following many movements and found the same result every single time.
It's too bad the stuff retails at around $10/can, because it actually works very well. And NO, I am in no way affiliated with the product or anyone involved with it.