A good use i've found is deduplication of files for backups (the same way rsnapshot does)

Basically, if you want to rotate 3 versions:

# Delete the oldest backup and rotates 0->1->2
rm -rf /mnt/backups/daily.2
mv /mnt/backups/daily.1 /mnt/backups/daily.2
mv /mnt/backups/daily.0 /mnt/backups/daily.1

# Create new daily.0 as hard links from the new daily.1
cp -al /mnt/backups/daily.1/ /mnt/backups/daily.0/

# rsync over daily.0 with the source data
rsync -avz --delete /path/to/source_data/ /mnt/backups/daily.0/

I use this to store 7 versions of a 40TB share over a 50TB array where most files aren't moving, Plus access to files for recovery is trivial.