I use ZFS on a dual-boot Mac to cross-mount the Linux partitions on OS X. ZFS is pretty much the only file system that allows this: The XFS OSXFUSE plugin is read-only, the ext plugin only supports ext2 with unstable write support and BtrFS can't be mounted on OS X at all.

The ZoL-derived OpenZFSonOSX port inherits ZoL's maturity, runs in kernel space and the OS X integration is really nice (Notification Center integration in ZED, custom icons, etc).

Lovin' it!