Really? I used MC edit to pose the file into a new world on the latest 1.8 and all the command blocks work fine. There is 2 command blocks in the beginning which place redstone torches where needed to start the very long repeater clock, a command block with the clock that is "commandBlockOutput false" so you're chat section doesn't get spammed with command messages. There is 3 command blocks under the exit bits of track, 1 is "tp @a[r=2] ~2 ~0 ~0" 2 is "kill @e[type=MinecartRideable,r=3] and 3 (under the hopper) "replaceitem minecart ~0 ~1 ~0.
I am not sure if these are exact but I hope it helps :)
Roller Coster Of Doom (1.8) on February 19th, 2015 11:07 PM EST