There is one unintended consequence of your new smb.conf. You turned off allowing guest access in usershare ( or simple sharing or nautilus-share or whatever it's called ). It's the section of the original smb.conf that looks like this:
# Setup usershare options to enable non-root users to share folders
# with the net usershare command.
# Maximum number of usershare. 0 (default) means that usershare is disabled.
; usershare max shares = 100
# Allow users who've been granted usershare privileges to create
# public shares, not just authenticated ones
usershare allow guests = yes
Given your requirements of having some with read only access and others not you probably wouldn't want this capability. But if you're in a hurry and really need to share some data between two boxes, there's nothing like right clicking on a folder in nautilus and basically saying "share this now" - especially if you're behind the safety of a router.EDIT:
Now that I think about it, I don't know if Mint5 has usershare capability but Mint6 does.