It was my understanding that both Unix and Windows used advisory locking, and had the same basic set up of read locks and write locks.
The only big diffrence that I know of (besides some file systems locking issues) is that most programs writen for windows obey the advisory locks. When Word decliens to open a file that is in use notepad will open it without trouble (unless it's to big).

Besides the argument that Windows might make it easyer to obey or harder to ignore file locks I don't really see where the diffrence is. You can still ignore them if you desire to.