In ego death, your sense of being the controller of yourself (including, paradoxically, your thoughts and, therefore, the very act of controlling yourself) is dissolved. The dissolution of borders between yourself and everything is a pleasant side-effect.
Michael Hoffman (no relation to Albert Hofmann) introduces his Cybernetic Theory of Ego Transcendence at www.egodeath.com. Recommended - this is the most fascinating web site I have read.
While psychedelics definitely facitilate this type of experience, they are by no means the only route. Religions also lay claim to it, but anyone who says his or her way is the only one is lying. Any priest or shaman must be presumed guilty until proven innocent. -Robert A. Heinlein