While one could argue that Time Machine makes 3-rd party cloning solutions somewhat redundant, there's positives and negatives to each. SuperDuper! has always been very reliable, and has been offering both incremental and full backups / bootable copies, scheduling and other features, while retaining a straightforward, uncomplicated user interface for well over 10 years. It has its advantages and disadvantages, compared to Time Machine, but in terms of reliability, it's as reliable a backup and cloning solution as Time Machine.
If you don't care for smart / incremental backups and other useful features, you're welcome to use the app without a registration for as long as you will: it will do the job as a basic cloning solution with or without a license, but a license acquisition will pay itself through the addition of said (very handy) features, referred above.
The Shirt Pocket upgrade policy is among the very best there is. Unlike many a developer, Dave doesn't look for ways to charge for version upgrades: the license key procured 10+ years ago, is as valid for the latest version as it was at the time of purchase some 10 years ago. Customer support is top notch, too.
There's also the nostalgia element, that I imagine is - of subjective value and won't do much to most: I tried SuperDuper! first, after researching Mac OS X cloning solutions and reading a number of raving reviews in the process back in early 2000's (somewhere between 2005 to 2007). It was acclaimed to be the best cloning utility back then, edging the likes of the Carbon Copy Cloner and others on accuracy and reliability. The app was launched onto the market in the early days of Mac OS X itself - many apps have come and gone, but SuperDuper! is among the handful still going strong today. Those nostalgic days of late Steve Jobs' keynotes, of Apple struggles to stay afloat, the days when barely one in 15 computer users owned a Mac…