Best one out there, and heres why:

Every other backup system that Ive tried only backs up the most commonly used fields. This one, however, backs up every single field, including all of your custom fields!

This app is not only great for making backup copies, but I also use the Excel backup spreadsheet as my desktop PIM. Its a very fast and convenient way to look up contact information when Im on by desktop.

CharFeld about Contacts Backup - IS Contacts Kit