I'd like to add a bit of information to make the above clear:
Manual focusing would not be a problem if the camera autofocus sensor gave some confirmation when I reach exact focus. After all, that's how I used this lens and some other manual Nikkor lenses before (on a Nikon F4).
Unfortunately, that does not work. The Olympus camera bodies apparently do not activate the AF sensor(s) unless a lens is recognised.
Much more information about this in an article by Andrzej Wrotniak at http://www.wrotniak.net/photo/oly-e/any-lens.html
(great read & site, BTW).