Previously on port-sparc I wrote:
>Not sure if this is sparc64 specific, that's the only netbsd system
>I'm using amd with.  

Ok, as a data point, I just setup amd on a NetBSD/sparc (1.5) and 
NetBSD/i386 (1.4.2) with these same maps and everything works fine.
How this is losing on sparc64 and only for this one map, I'm not sure
but it is. 

Just in case, this is the version of the home map I used here:

/defaults       opts:=rw,grpid,intr

#               /home/localhost always points /home/<machine>
localhost       type:=link;fs:=${host}

zen             host!=${key};type:=nfs;rhost:=${key};rfs:=/d2/users \
                host==${key};type:=link;fs:=/d2/users

*               host!=${key};type:=nfs;rhost:=${key};rfs:=/usr/home \
                host==${key};type:=link;fs:=/usr/home

which is the same as the one I previously posted with  corrected
server and path names.

--sjg