I read that snapshots will be introduced in OSX Lion, I don't know if they're somehow related to ZFS snapshots,
though the "we can do it better ourselves" sounds very microsofty.
ZFS addition in OSX by Apple itself would have been greatly appreciated.
Lion still uses HFS+. They seem to be doing some trickery to save space (i.e. they don’t save complete copies) but it’s all still HFS+.
I wonder: is it something like how Time Machine works? In that each file is mirrored and unmodified ones are hard linked through editions? I can't imagine that being space efficient but I wouldn't put it past them. AFAIK OSX doesn't have an LVM equivalent in terms of snapshotting live file systems.