I use SyncBack every day. It just plain works. I back up accounting's files onto my computer daily and automatically. That way I am not working with their files in case I change something.
My home network drops to it's knees when I copy files through wifi from my laptop to the big desktop drives. I was dreading copying my picture files over and wondering how I would sync them because some of the files had already been copied over. I installed SyncBack and let it work. It took 54 minutes but I could not even tell it was using bandwidth. Super program.
http://www.2brightsparks.com/freeware/freeware-hub.html