The developer docs shed more light on the features: https://developer.apple.com/library/prerelease/content/documentation/FileManagement/Conceptual/APFS_Guide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40016999-CH1-DontLinkElementID_27
Sensible. ZFS has a number of features which make little sense for Apple. How many storage pools does the typical Mac have? Just the one. At the same time, a design that expects a gigabyte or more of memory is a liability even on an entry level MacBook, to say nothing of watches. ZFS also requires quite some spare space for decent operation and a lot of people likely run their iPhones at 99%.
The semantics seem like a COW file system. Hopefully it’s a bit more than the equivalent of ZFS with the ARC turned off.
Ars now has a more in-depth look at the new FS at http://arstechnica.com/apple/2016/06/digging-into-the-dev-documentation-for-apfs-apples-new-file-system/