Me and a few buddies rode out to Bromley this summer and rode the "sun mountain flyer" zip line. To me it wasn't particularly thrilling/exciting and I think it was $20/person. The guy working it was chatting with us and explaining how the "sled" that holds the swing seat/harness works, there's like a centrifugal clutch in it that starts to drag(brake) once you reach about 30mph. The braking wheel is on the back, so if you lean forward you can go a little bit faster. The actual ride lasts about 30 seconds. If you want to race(there's two lines), make sure you take the left one...every single time that person won by quite a bit. A couple of the other guys thought it was a blast though, and my perspective might be skewed a bit. For one, I ride a Vmax, and two, I'm a nut for roller coasters. Went to Cedar Point twice this summer, and once to Six flags NJ. So I need to be haulin' ass to get a good thrill. And vboost is a lot cheaper than a $10mil roller coaster.
Actually if you go to Bromley I'd recommend the death sleds. They're little tiny carts you sit on with one handle in the middle and ride down a really, really long track down the mountain. If you've got a pair that clank you can make it down the entire track without using the brake(except for at the very end to get off). You push the handle down to lift the cart onto it's front wheels, letting go of it splits the front weight 50/50 between the brake puck and the wheels, and pulling back lifts the cart onto the brake. The fun thing is that the track isn't idiot proof, like there aren't lips at the top of the banked turns to keep you from flying off the track. I don't know how fast you go, but I'd imagine at least 30-40 in spots. On a piece of plastic with four toolbox casters under you, that's pretty fast. Have to bring a handheld GPS next time and see. Only thing that sucks is more often than not you'll be going so fast, you'll catch up to some mom+kid riding the brake the entire way down going like 2mph. Try to BS around at the top and hold up the line a bit to make sure the previous person is almost done before you go to avoid "traffic". Also, I think you can buy a pass for unlimited rides for like $15 or something.