I have used SuperDuper! for more than a year now, and it always worked for me.
I use it together with TimeMachine. I made two partitions on a new disk. The bigger for TimeMachine backups, the smaller for a bootable clone of my system, which I made with SuperDuper! The frst clone takes long, as expected, but then it is easy to update it with SuperDuper! SmartUpdate, which copies only the files that have changed. This can be very fast.
It is so easy to perform a smart update, that I can always perform it before a system upgrade, so as to have a fall-back position if anything goes wrong.
My clone also saved my work a day that I had an I/O error on my startup disk, and couldn't boot my system. I booted from my clone, than erased my internal hard drive and copied to it the content of my clone, then I rebooted from my internal drive.
This alone is enough for me to appreciate SuperDuper! very much.