Can't say i've been on a rollercoaster in a very long time, but as a kid I was never too keen on them going upside down, preferred the whole going quickly and up and down thing (ie- roller-coasting), but maybe i'd still enjoy it. I loved playing Rollercoaster Tycoon 2 though, spent a lot of time on that game.
I hate 'em. I just dislike headaches and puking and screaming, I like fast stuff, and heights are no problem, but those three, they just piss me off.