My two cents on usage:
Soft links may be used to shorten long path names, i.e.:
ln -s /long/folder/name/on/long/path/file.txt /short/file.txt
Changes made to /short/file.txt will be applied on the original file.
Hard links may be used to move around big files:
$ ls -lh /myapp/dev/
total 10G
-rw-r--r-- 2 root root 10G May 22 12:09 application.bin
ln /myapp/dev/application.bin /myapp/prd/application.bin
Instant copy to different folder, and original file (on /myapp/dev) may be moved or deleted, without touching the file on /myapp/prd