Yes indeed, for a very comfortable way of dying, its hard to beat apoxia...general well being, don't care, pleasantly intoxicated (that word contains the essence, doesn't it!)
If you are a smoker, generally fat and unfit, getting on in years, a functioning oxygen system will certainly help....it is also good for hangovers.
My first experimental flights at altitude in a glider, at Deeside gliding club, I was floating happily in the wave at about 14,000, with the oxygen system turned on half way between 2 and 4...found out later that this halfway meant there was NO OXYGEN being supplied. Luckily my flying skills had declined somewhat and I was unable to maintain altitude, so descended to lower levels.
Never did like being dependent on systems that can be screwed up by simple mistakes!
So when I did eventually manage to achieve diamond height, at 20,300 feet above the airfield, that was it, never again. Don't like scuba diving either.