I've been considering this too. I used to take a lot of Ecstasy in my youth and had one time where I blacked out, I think unconcious and although I was sweating like crazy I can't say it was a wholly bad experience as by the time my head fell back onto the back of the seating (I was in a nightclub) I think I was too far gone to feel pain or regret. I just remember thinking I'm going... and then coming too, how much later I don't know, with my head flipped back over the seating. Whether there was something else in it that caused the situation I don't know but when I came too and managed to get some water I felt lie I needed to take another one, which I did and actually felt fine afterwards, almost like being refreshed, I got up and danced for the remainder of the night.
But then I've had lots of other times when I've not had bad experiences from taking too much or a really bad one but from one just dodgy enough to make me feel on edge.
If I'd have died on that bad one I can't say I was aware of major discomfort or pain. I was aware something was going wrong and I didn't feel good but I wasn't capable of doing anything about it. What the dosage or any other ingredients were though, I couldn't say. It was around 1995.