I'm 6'4 and I've never once been checked. They have a height stick over by the ride fluffy, fluffy bunnies filled with medicine and goo but they don't really pay any attention.
As someone who is 6'6", I went into my first trip to Six Flags New England with high hopes that my height wouldn't be a problem. Unfortunately, I was unable to ride Superman, Goliath, Mind Eraser (thank god), and Gotham City Gauntlet(?). Not sure why I wasn't able to go on Gauntlet, but I always will abide by the rules and would hate to cause a scene at the ride and slow down operations. Nevertheless, Wicked Cyclone was a really really well-put-together ride, with, in my opinion, a perfect blend of elements(great job RMC!) All in all, still a good day trip even though I was not able to ride Superman.