I got FreeBSD running on a Raspberry PI. It isn't too hard to install and get up and running. I primarily use FreeBSD on the Pi for ARM assembly programming. All BSDs are great for devs.
ooc why didn't you try NetBSD? Isn't running on every little device kinda their wheelhouse?
I did try NetBSD first on the Pi but the install wasn't working for me. Getting FreeBSD up and running on the Raspberry Pi was a lot less painful. If I really want to kick around NetBSD I can run an instance of it in GNU Boxes on one of my Linux boxes.