I’ve been using SD! for (almost exactly) one year now and it has saved my bacon several times. SD!’s Smart Update feature is so fast that it is painless to run before applying software updates. Being able to revert after discovering an incompatibility (which often happens with Xcode or WO updates) is a godsend.
Now, Shirt Pocket has rewarded my loyalty by updating SuperDuper! to version 2.0.
SuperDuper! 2.0 includes scheduling and other enhancements (the press release with all the gory details can be found here).