On those dives, I never felt any different than I did at 30' -- no delayed reactions, no short/long term memory loss, no anxiety, no feeling of "over-enjoyment". Bare in mind that nothing ever went wrong, and there was never any unusual exertion going on those utterly foolish air dives . Bottom times were in the 20-30min range in 40F water (Lake Superior). I have no doubt that narcosis was just lingering there (like Murphy) waiting for something to go wrong, so it could unveil its ugly face.
One thing is for certain, deep air diving ranks up there with drunk driving. We get a lot of close calls up here and few deaths once in while due to deep air. On top of the narcosis (both CO2 and N2 narcosis) that is going on, you simply cannot properly deco off of air. Using deep stops, slow ascents, 50/50, and O2 helps, but the bottom line is that helium is better in every regard from a safety stand point.
Mike