The two things that got me about the experience was
#1) After I had puked for the Googleth time and had nothing left to give and feeling like my head was going to explode. I was lying there being genuinely concerned that this is the time I am going to find out if I have an un-diagnosed Brain Anurisim or heart condition because, if I did, this might actually kill me!
#2) The other thing that shocked me was the sheer speed of the onset. I went from;
Fine>Feeling a bit odd>completely incapacitated with Uncontrollable Puking.
In no more than 20-30 seconds!
If I had been driving on a Motorway, I would not have had time to pull over to the side of the road and stop safely.
It was really that fast.
Fortunately I had "Just" got home before it struck me. How I would have managed had I still been out and about I really do not know!