if you have ever been in the middle of a giant file copy between drives or computers, then gotten an error, and then had to start over without knowing where you left off, you should get this. i love super duper and carbon copy cloner but this is different. this lets you be a lot more specific, it keeps things copying even if there's an error (the operating system and rsync command don't give you that luxury) and it will copy between different file systems, like between your mac and a fat32 formatted external drive. no one else will do that in my experience. anyways i love it. i haven't gotten into the agent or hardcore stuff, just used it like a dummy and it has worked flawlessly.