In terms of horrible personal biological experiences, vomiting is second on my list, but passing a kidney stone is about 100x worse.
I think puking is way worse for some people than others. For me, not only is it a physically painful experience, but I'm rough ridin' loud when it happens. I've got no control over it. My wife, on other hand, is a more silent, nonchalant puker (and not in a bulimic sort of way). She was feeling sick a few months ago, got out of bed, went to the bathroom, and then started brushing her teeth. I was like, "why are you brushing your teeth?" and she told me she had just thrown up. Didn't hear a thing.