Got my RPi on 2012-April-19. Currently running the customized Debian image, since I know a little more about Debian than the other supported distros (Arch, Fedora).
One of my project ideas will be to get ArmedSlack running on the RPi. I would think that the Debian kernel and modules, with ArmedSlack userspace, could be hacked together to work, but that's only an uneducated guess. ArmedSlack currently has three installer images, for the three supported platforms; I eagerly await the fourth, Raspberry Pi.