Interest in seeing HAMMERfs ported to FreeBSD?

IMHO it would be nice. It is a filesystem with a lot of advanced features that is less resource-hungry than ZFS. Always IMHO, in some situations can be really useful.
This is something that has come up a few times since HAMMER's introduction. I remember Matthew Dillon commenting that it's certainly possible to take parts of the DragonFlyBSD code, but that there are also significant differences between FreeBSD and DragonFlyBSD that would require quite a bit of work and knowledge of both systems to port things to FreeBSD...
I would sooner like to see HAMMER(2) on FreeBSD than btrfs. But that's only me. Maybe the best way forward would be to partly pull in some changes from DragonFlyBSD, like the locking tockens. These sound really interesting and likely would make a lot of interesting stuff possible.
I think with the Btrfs comment, Crivens was pointing out that Btrfs will soon be available to FreeBSD users through the Linux-kernel-as-a-library feature. This should allow anyone on FreeBSD to run any Linux file system (including Btrfs). So we're likely to have Btrfs on FreeBSD long before we get support for HAMMER.

Personally, I don't have strong feelings about HAMMER one way or the other. It seems to supply the same features ZFS does and ZFS works well for me. I can't see myself switching. But, as others have said, it's always nice to have options.
Slightly off-topic: My favorite aspect of all these next-gen filesystems---ZFS, BTRFS, HAMMER, ReFS---is that they all have similar goals, purposes, and methodologies, all have their own solid user bases, and all are designed to be eminently future-proof. Go back a few years, and you'll find people proselytizing for their favorite OS because its next-gen filesystem makes it (or will eventually make it) "better" than the alternatives. In five years, every OS will have its own filesystem that does pretty much the same damn thing as all the others. It's convergent evolution, and it's awesome. While I definitely like the BSD license more than the CDDL, and would love to see the Dragonfly folks get credit for doing their own (admirably difficult and relatively unique) thing, ZFS and FreeBSD just make sense to me. When I chose to switch from Linux, it was largely because I saw FreeBSD as a clean and fine-tuned combination of the best parts of my most respected Linux distros, and ZFS as a better version of BTRFS.

I also personally like the idea of an operating system having its own filesystem fairly well-integrated into its core components, making it feel like a "natural" part of the system. HAMMER was made specifically for Dragonfly BSD, ZFS was ported to FreeBSD in such a way as to integrate it with GEOM and the FreeBSD sysctls, and from what little I've read the OpenBSD folks would like to port HAMMER2 in a way that fits their own core values and OS design. Linux has BTRFS, and ReFS will give Windows folks a native solution much of their less technical user base can rely on without a separate server/appliance running an unfamiliar OS. Everyone gets what they want, which is an operating system they enjoy and believe they can rely on, with its own filesystem they believe they can rely on.