When they do, they report of the fascinating experiences they had while they no longer identified themselves with their bodies. And interestingly, the descriptions are remarkably the same.
Dr. Raymond Moody discusses this in his book Life after Life, where 100 people tell their story of dying and then coming back to life.
One of the interesting consequences of crossing over to the non-physical is that when they return to the physical, people feel renewed sense of the spiritual basis of life and a deeper sense of purpose.