I've been using elementary os for a while and met plank dock with elementary and not having a magnifying effect like the one in the os x has been bugging me since, so I've made a few modifications on the source code and I've made a working magnifying effect.
Although, I know that the magnifying effect on the OS X is slightly different, like magnifying the whole dock instead of just the one you are hovering. I could achieve that but it would take so much modifications and I'm willing to commit these changes to the official repo, and I didnt want to alter the code so much.
Source details are on my blog:
http://blog.fatihbakir.net