I have some Mac users connected to NW6.5 servers (SP3 and 4) that
complain that when a mac user copies a file to the server other users
might not see it for a while, or it might appear immediately. Most just
log in and out again to 'refresh' the volume.

I am applying the wsock6h patch (or SP5) to these servers - should I
wait and see, or is this a known issue with a solution?

Hard to get accurate accounts of this issue - mac users don't seem to
complain much. I first heard about it by accident (overheard a
conversation in the elevator), after asking around - most of the mac
artists experience it from time to time.