I picked up a license for Econ Technologies' ChronoSync a little while ago, as I didn't want an app like SuperDuper which simply backs up an entire machine. ChronoSync offers a ton of options for fine-tuning your backup operations and synchronizing a machine with a backup folder or even another Mac, scheduling backups / synchronizations and even backing up to optical media. ChronoSync also has special options for performing operations like syncing Home folders between Macs, and even backing up to an iPod. Long story short: if you're looking for a highly flexible backup solution, I definitely recommend ChronoSync.
The one catch with ChronoSync can be summarized with a twist on an old phrase: with great power sometimes comes great confusion. ChronoSync has a slight learning curve due to all its flexibility, but thankfully, 43Folders just pointed out a great ChronoSync Tips page with backup scenarios for a number of different users. Listed on the page are a dozen sets of instructions with screenshots for setting up operations like synchronizing/backing up iPhoto, synchronizing to a disk image or another Mac and even using the Document Scheduler to automate as many different backup and synchronization operations as you can dream up. For anyone trying to wrap their head around what ChronoSync can actually do for their backup and synchronization sanity, this is a great one-stop case study page that should convince any potential customers to take the dive.