A guy from MDL has extracted the cab from windows server 2012 to bring the deduplication feature in W8 x64 (it cannot work with W8 x86).
I gave it a try on the W8 enterprise trial and it works perfectly. Space savings depends highly on content type, giving very high space savings for VM and less for documents files or already compressed files. It can be enabled on external storage devices (external HDD). Doesn't work on system drive and I haven't tried on flash devices.
More info and instructions here: http://forums.mydigitallife.info/thr...ws-8-x64/page5
It is compatible with NTFS compression and Bitlocker.