Slime block duplication glitch still exists in 1.8. I built an exact replica of the slime block elevator given in the link below but I cannot use it because as the platform moves up or down the slime blocks duplicate making it impossible to use for the next time.

This glitch existed in pre-release versions and I hoped it would be fixed in the official 1.8 release however I am still getting the same problem.

https://www.youtube.com/watch?v=_-FiInNNGs0