OK, so this past weekend I upgraded all 9 storage nodes to 8.0.1.5, while 
leaving my NW server at 7.6.2. All worked fine, as the Readme says it 
should. I did have to do 3 things:

1. I had to add "save -a "'ignore-all-missing-system-files=yes"' to all my 
NW 8 clients (not just the storage nodes), otherwise the ALL directive did 
not work. Seems that at least 50% of the time, the NW client failed with 
that error on the ALL directive.
2. As I expected, you have to (well, should) delete the NSR peer 
information on the server for the updated clients.
3. The default installation path has changed for NW 8. It always used to 
"\Program Files\Legato\nsr" (on Windows); now it's "\Program Files\EMC 
Networker\nsr". You can redirect it back to the original path (as I did, 
when upgrading a Workgroup Edition server, so it could find all the server 
history). Not a big deal, but if you have scripts that check the old 
location, you may need to modify them.

Otherwise, it all seemed to work. Now I need to finish re-licensing my 
hosts. Then I can rename my main NW server, then upgrade it to NW 8. Then 
I can upgrade the remaining clients to NW 8 at leisure.