I just did my Nitrox cert (for which the DS included two dives) and I'm sold on this. Did two dives yesterday, 3 shore dives with long surface swims today and I feel great. No hunder and not at all sleepy. I know this is not one of the advanatges of the gas listed in the learning materials but normally I'd be napping al day. Even though I've never seen anyone dive Nitrox here in Colombia I'm going to start just so I don't get wiped out, my non-diving gf will apprecoate me not sleeping all day after my dives.