Mirror couldn't be simpler to use, and couldn't be more handy. Put simply, this free program does is what it's named--it mirrors, i.e. copies a folder structure to another location to another. After a folder structure (e.g., My Documents and all its subfolder) has been copied initially, only added or changed files are copied--which makes it very efficient, i.e., fast.
The Mirror interface consists of single dialog-like window with Source, Target, Help and Mirror buttons. The first two buttons open file dialogs where you define what is backed up and where it's backed up to. Click on the locations listed to their left, and a window to them will open. Help is obvious and Mirror invokes the backup.
There are only three options: Synchronize target (remove files in target location that don't exist at the source location), Minimize (the window--while running), and Auto exit, or exit after finishing.
The program worked fine in my hands-on, and it can be invoked by a script. My only real complaint is that long location listings are truncated (wrapped out of view, actually). If your backup needs can be met by a simple incremental copy routine, then this tiny utility fits the bill.