I am currenlty running 'make installworld' in multi-user mode.  I was considering just going into the client's office (its great when a client gives you keys to the place) early tommorow morning re-booting into single user mode and then running it but that made no sense to me....any file in use that might be over-written by a newly compiled binary would be in memory.  It seems like the Handook's recomendation of rebooting into single user mode seems like paranoia....personally, unless this thing freaks out on me during the week I will continue to do it this way.  Well, I feel like that was a rather pointless post.  I just hope that some poor soul upgrading a FreeBSD via ssh on Sunday night will be able to find this post and see that yes, you can run 'make installworld' in multi-user mode.