Amazing, one of the best experiences one can go through if you have the right understandings to do so. Now before anyone says you can't die and come back let me assure you you can, through meditation, and you do not enter just into a death state, you enter into a state that by all medical understandings and knowledge you are dead, thus no pulse, no heart beat, and if you stay in it too long the body will go into that smelly state we love to call decay.
Okay, so for those who want to attempt working towards something like this i recommend you get the Tibetan book of the dead, just because before one can attempt physical death you have to manage to attain a full state of ego death, only from that point on can you use all the understandings gained from ego death and take them to the next step which is death on command.
Here is a brief description of my own two death experiences thus far, the first one i systematically switched off the body with ego death, then withdrew all my energy and conciousness from it and then allowed my entire being to dissolve away into nothingness, into a state of dark ego death, as one goes through this you truly do see your life flashing before your eyes, depending how much karma you carry these flashes can last for minutes or hours, once one has moved through them you reach a state of singularity where it feels like everything is compressing down on you, everything in existence, and as you let go you feel yourself slipping away, as you slip away you see the most amazing patterns and images due to a DMT release caused by the pineal gland, this only happens on very special occasions like birth or death. Then you reach a break, and the body no longer exists, nor does it matter, and all that there is is quite peace, trick is basicly programming your own conciousness before attempting it to give you a yank back when the body starts needing life within it again or else the blood will stagnate etc and the body will start to decay slowly but surely, if you stay out of the for more than 2 mins on your first succesfull attempt be aware that when you get back in it will feel as if your entire body is one giant cramping muscle due to the lactic acid buildup in the body from now oxygen circulation.
Second experience was from pushing out energy so hard that the entire body shuts down due to the physical tension within it caused by the pushing, this method actually causes energy ripples which can be used to do some pretty amazing things, but it is a different topic. when one pushes to the point of full ripple the body shuts down and you seperate from it,the body once again goes into a death state where by all account it is dead, but one can regard this state achieved through ripple like more of a state of suspended animation. As you achiev the state do you begin to see the axioms which form physical reality and the perceptions which form perceptive reality, and as most people who work with energy manipulation knows, what you see you can start to effect, which opens up quite a few doors if you understand it...
Sorry for going off on a tangent, in a nutshell death is one of the most amazing experiences you will ever encounter, learning to art of dying before you are forced to die at the end of your life helps you make peace with death, each experience towards either ego death or physical death will bring with it understandings which can be used in various parts of life and life of the soul, once you have walked both sides of being, both life and death and returned happy from both you will truly understand why people say death is only the beginning.