Firstly it backs up. Useful, but there are other manual ways. Still a lot faster. Then it can back up to remote places such as Amazon S3. More useful, and probably more secure. Plus... contingency.
And now, it can backup a dev site, and transfer it to a live site without screwing it up. You can tell it not to overwrite usertables, comments or forum posts. Now that's EXACTLY what you need.
His tutorials are well written too.