The term is obviously a bit of a misnomer and gets a lot of people confused.
I actually think that in a complete ego-death state there isn't really any differentiated consciousness beyond the just 'being', so there isn't really that much to experience about it. But the really jarring part is transitioning to and fro... and also usually the state is not entirely complete and there still remain parts of the self-awareness intact. I have only once been in a long-lasting psychedelic ego-death. But I have had many more transient states of advanced ego dissolution.
In ego death self-awareness ceases but self-awareness does not equal consciousness in the being-awake sense. If you lose your sense of self, you can still retain general awareness. It is very abstract and difficult to explain what it is just to be, with your awareness stopping there. It is an absolute baseline state. We are entirely used to having some form of mental process or activity.
Typically IME timelessness (also loss of sense of space next to loss of sense of time) is experienced since every event is normally put in a frame of reference where you are a person who is experiencing event after event. There is no telling what happened or how much time passed during total ego-death since there is no frame of reference at all. The model of the world we have in our minds and experience as unmistakenably present is entirely based on that frame of reference just like the model of our 'self' is.
Casually considered there might not seem much difference between that and just being unconscious, but the existential / ontological relevance and how it relates to mysticism that is both very important if you ask me.
Max freakout is right: in this current context the ego is considered to be the model of our self and our sense of it which are completely co-dependent.
Also note that we have a centralized ego-death thread here:
http://www.bluelight.org/vb/threads/375388-The-Big-amp-Dandy-Ego-Death-Thread
There are 26 pages of discussion and 5 subthreads already! (This thread will be merged with the B&D later though perhaps this current thread is considered significant and we can close the B&D and use this one to be the start of part 2)
Some people might say that the discussion is just disagreement about an elusive or esoteric term, I think that it matters whether someone participating in the discussion has experienced it or not (I don't mean that in an elitist way, it is just more difficult to comprehend and accept if you have not been there), and the term is not meaningless but can tell us something about very basic, fundamental psychological or spiritual processes.
I surely won't pretend that it is something everyone should try to experience, but I'd like it if others don't devalue or deny its existence or validity either.