It's slow and buggy. The feature list has become so huge that it's nearly impossible to figure out. Sync Pro "forgets" hard drives and can't be trusted to back up automatically. I've used their cloning product, too-- Backup Simplicity. It's a nice clone app; except sometimes it "forgets" to backup.

I've had better success with Super Duper.

I've used SD for nearly a year and find it wonderful. It's a great Mac utility; elegant, with many features, not one of which gets in the way of what you want. The learning curve is perfect. Simple for basics, step-by-step to more features.

Here's a review I found that says the same thing:

http://www.mac360.com/index.php/mac360/more/my_favorite_mac_backup_utility