I've stumbled onto something that might be of interest here.  My B&W G3 
is one of those strange machines that worked with NetBSD 1.4.3 but 
experienced USB/ADB keyboard problems since NetBSD 1.5.  The only way I 
could get it to work was to boot with an ADB keyboard installed and 
switch to the USB keyboard after it goes multi-user.  The last version 
of NetBSD I had installed on this system was 1.5Y.

This evening I booted into NetBSD and the USB keyboard worked without me 
doing the ADB/USB dance!  This was with the 1.5Y system that I still had 
installed, and it booted this way every time I tried.  The ADB keyboard 
wasn't needed and wasn't even connected.  There have been no changes to 
the NetBSD I had installed, but there have been some changes to the 
Mac.  For one the mouse got fried and I had to replace it, but I don't 
think that had anything to do with it.  The mouse on this system was 
always kind of strange even under MacOS and that didn't change with the 
new mouse.  The other thing that "changed" was installing MacOSX along 
with all the updates.  Since that last MacOSX update my mouse has 
started acting civilized too.

I checked everything I could find in OpenFirmware and can't find 
anything that looks different, but that doesn't mean much.  As far as I 
can tell the MacOSX installation and 10.1 updates fixed something on 
this system that allows it to run NetBSD again.  Looks like it is time 
to upgrade to -current and see if the good luck holds.

Hope this is useful to anyone else having keyboard problems with NetBSD 
on their Mac.

-bob