And there is http://code.google.com/p/maczfs/ and http://downloads.maczfs.org/
The truth is despite all the Siracusa "We Want ZFS" nonsense, it's an absolutely terrible choice for a consumer filesystem. All of the nice features come at the cost of it eating an enormous amount of RAM and CPU resources, and it's integrity guarantees are meaningless if the machine isn't running ECC RAM anyways.
Apple was never going to ship laptops running 10.5 where 4 Gigs of RAM were immediately eaten by the filesystem and battery life was halved from 10.4 due to the extra CPU load. ZFS as the default for OS X was always pipe-dream nonsense promoted by people with no understanding of or experience with ZFS.
As for memory, the minimum you need for pre-fetching is 2GB of free RAM. ZFS will, however, run on less with pre-fetching turned off.
The thing with ZFS is that it will consume your RAM and CPU if you have all the uber features enabled and a boat load of pools created, but since you don't need nor want that on a desktop, ZFS shouldn't need to be that resource hungry.
What's more, part of the misconception of ZFS's bloat comes from the age of the file system. My original ZFS server was less powerful than most budget laptops these days (and I was running a small number of VMs off that thing as well)! So modern systems definitely do have the resources to run ZFS as their desktop fs.
HFS+ hasn't exactly failed me spectacularly, but I'll be more at ease with my sensitive and valuable data on ZFS.
