It could be a timing issue depending on where you placed the script. I use an upstart job to do this sort of thing:
Create an upstart job named "bind-to-home-folder.conf"
With this content:
gksu gedit /etc/init/bind-to-home-folder.conf
"start on stopped mountall" means that this job will not start until all system partitions in fstab are mounted first. Symbolic links are easier to set up but Samba does not allow a client to pass though a symlink unless you do something that samba regards as insecure and I use Samba. In any event it's just another way not necessarily a better way.
# Bind folders to home directory
description "Bind folders to home directory"
start on stopped mountall
mount --bind /media/Users/user/Pictures /home/user/Pictures
mount --bind /media/Users/user/Music /home/user/Music