CP Boy, don't worry, I know exactly what you are saying about heights. I love Magnum, but I'm still not crazy about heights either, but I am getting better about it. I rode the Giant Wheel last year and actually sort of enjoyed it, that is not real common for me.
However, like you said, you get to the top and you head right back down. Guess what, that is exactly what Millenium Force will do. It will get you to the top and then send you back down, and just think, you'll get back down much faster than you would on an elevator.