I would say it is definitely more than sleep-deprivation alone. I've had chronic insomnia most of my life (but not to the extent of staying up several days on the trot without the use of drugs - 2-3 days at most and usually more a case of just not getting much sleep) but have never experienced anything like the extended peevcalm state. There have been people who've stayed awake without using drugs even longer than the average peev binge but none report anything similar to the Zen thing. Confusion, hallucinations and paranoia - yup. Calm, timeless, singularity - nup. I'd say it was down to the peev and the peev alone. No other stims seem to replicate the effect no matter how many days you're up for. Desoxy would be about as close as they get and even that isn't all that similar just more similar than anything else I can think of.
never tried desoxy, apart from taht i can only agree with this post.