Talking about complete OS:es I run Ångström linux on my PI, I love Ångström and a few mods you can get the PND support and run most OpenPandora programs (recompiling may be needed), so if looking for an alternative experiance which tho requires some more tinkering I recommend Ångström.
If I had the spare time I would love to rebuild the OpenPandora rootfs for the PI, to many projects to little time
