NetBSD.
It is workable. Coming from the Linux world, I found the first steps
disorienting. I am posting via wireless, and even the sound system is
in pretty good shape (although I haven't figured out how to get output
from the headphone jack).
Whether compiling all this stuff was really worth it, I can't quite say. Dependency resolution does have its place, though. I look forward to a version of NetBSD (or any BSD) with decent support for that hoary G5 PowerPC Macintosh.