>	Now the machine is listing all of it's devices, but still isn't up and
>running.  At this point I get the root device prompt, and the cursor is 
>actually
>shimmering (as if it is being redrawn continuously).

Because the USB keyboard driver doesn't have console support.
Apply ftp.netbsd.org:pub/NetBSD/arch/macppc/imac/iMac.ukbd.diff.
(umm, wrong name...)