I've got a Linaro build running on mine. (It arrived on the 24th, so I had a good Christmas!) it's actually stable overclocked to 2GHz and the Mali in it is also stable at 800MHz.
After that, it's just like every other rootfs. I focus on Gentoo, so other distros... I don't know, but they will have an Ubuntu image up soon.
There are no graphics until X though, so you're stuck with ssh or serial console until then.
Kernel sources come from the BSP download on hardkernel's site. Should be a tarball in there named kernel_4412.tar.gz