I did notice that the presence in my $HOME of a directory called .gvfs prevents to cleanly mirror it with rsync. This occurs in some situations if the gvfs package (which is included in Slackware) is installed.
After a little googling it seems to be a fuse file system that can't be read nor removed by root, at least with the initial Slackware settings.
I have seen proposals for setting or updating udev rules to avoid that situation but the simplest IMHO is to unmount then delete it. I do that just before I launch rsync. As root:
umount /home/didier/.gvfs && rm -rf /home/didier/.gvfs
Maybe there are security concerns in doing that, so if you are aware of any please answer this post.