That Leopard would support Sun Microsystems'
ZFS was known for several months, since a screenshot from an earlier α release of the upcoming version of OS X was leaked late in 2006 showing support in the Disk Utility. At the time of that leak, several developers reported that 10.5 did not support ZFS as its
default filesystem, meaning it could not boot from it or use it for the system partition. Well, now it can. Jonathan Schwartz, Sun's CEO claims that ZFS is going to be the default filesystem on Leopard replacing the ageing HFS+ Journaling. Great news for the Mac and further proof of the value that Open Source software adds to commercial products.
[P.S.: Schwartz's video is quite interesting for FOSS and Sun customers too. I'll have to revisit the topic of Sun Microsystems and its relationship with Open Source in an article some time.]