For some of the non-duality/direct path people sleep is important.
http://non-duality.rupertspira.com/read/deep_sleep_death_and_reincarnation_essay
http://non-duality.rupertspira.com/read/the_highest_prize
http://non-duality.rupertspira.com/read/the_experience_of_deep_sleep
http://webcache.googleusercontent.com/search?q=cache:Te-Lqc_vfV8J:www.nondualitymagazine.org/nonduality_magazine.4.greggoode.interview.htm+&cd=1&hl=en&ct=clnk&gl=uk&client=firefox-a
(original interview down so this is a cached link)
A quote from this interview is below - which might be interesting for users of this forum:
NDM: Getting back to the direct path. One of Sri Atmananda's methods was an enquiry of an everyday experience that is accessible to all of us. He regarded deep sleep as a ‘key to the ultimate’ and said that if a student is ready and able to seriously contemplate and investigate deep sleep, then this alone is enough without the need of having to experience or to spend years cultivating nirvikalpa samadhi.
If this is true, then what is the point of yoga and nirvikalpa samadhi? Isn't the ultimate goal of yoga, liberation, brought on by having experienced nirvikalpa samadhi?
Would you say there is a difference with deep sleep and nirvikalpa samadhi?
Greg Goode: Each tradition will naturally give pride of place to its own activities. The yogic tradition, which crosses paths with traditional Advaita-Vedanta in places, says that there is "light" during nirvikalpa samadhi and "dark" during deep sleep. Deep sleep is thought to be a dark covering over the Atman, which is the true Self.
But in the direct path, any object or state is a temporary appearance to witnessing awareness. So What about those moments when no objects are arising, and there is just objectless awareness? This is exactly what deep sleep and nirvikalpa samadhi are. One is in the middle of the night. The other is in the middle of a meditation session. For the person doing self-inquiry, deep sleep is more accessible!
The value of these moments is this -- you experience that you are not any object in the world, body or mind. Why not? Because you are present as "I" in the absence of all objects. This provides experiential proof that you are the awareness in which objects arise.
So from the perspective of the Self, would not this dark covering or veil of sorts of the state of deep sleep also be considered an attribute or object of sorts? Isn't the self nirguna?
