For backups, keep it as simple and easy as possible, unless your running a network or IT department. For home or small office use, the more complicated it is to do the backup, the less likely it will get done, and the less likely the backups will be usable/correct when you need to restore a file.

For OS X, use CarbonCopyCloner or SuperDuper. Carbon Copy Cloner is free, and SuperDuper is shareware. Only some of the features of SuperDuper work, unless you register it for $28.

For Windows XP or Vista, use SyncToy v1.4 from MicroSoft. It's a PowerToy that can synchronize (i.e. match file-by-file only the changed files) two directories. You need .NET 2.0 installed first, but you can install that with Windows Update. Download it here.