On one of my two rides I did get dizzy and experience some blurred vision between the pullout and getting around the first turn. I was clear-headed by the time I reached the Magnum hill, though. And my other ride was perfect. Guess I just wasn't positioned right or something :) The pullout is quite intense, though, and I'm sure it does unpleasant things to your blood flow for the couple seconds you're there.
Actually, the only ride I've ever blacked out on was Corkscrew :) It was waaaaaaaaaay back, when I was about 6 or 7, and it was the first inverted ride I'd ever been on...maybe my first coaster period, for that matter. My memory at that age is blurry. Anyway, just wasn't prepared for the inversion, I guess :) I remember going into the loop and then getting out of the train. Mmmm...gotta love missing time on a coaster :)